Isekai

"Hey guys, today I wanted to talk about the newest, hottest anime to come out this season. All right, get this: It's about a completely normal shut-in Otaku with a very specific skill set that makes him useless in the real world, who is suddenly transported to a fantasy world kinda similar to any JRPG you've ever seen where he suddenly becomes the hottest shit, and he has two jobs: Messing up any poor soul who looks at him the wrong way and getting some 2D bitches. Wait, doesn't this sound oddly familiar?"

– Gigguk, "Isekai: The Genre that Took Over Anime"

Proof that Japan has no publishing standards or quality control. Isekai is a Japanese word assimilated into the /tg/ lexicon from the weeaboo faggots at /a/ and /jp/. Literally meaning "another world" or "parallel world", it refers to a genre in which the main characters are from "our" world and taken to a foreign world resembling some form of fantasy game, where they proceed to become adventurers. Usually, plot reasons prevent them from heading home until something is taken care of - typically whatever big bad evil guy is threatening everything - but sometimes they're stuck there forever and have to adapt as best they can. Methods of transportation are vast and varied, including but not limited to: stumbling into a portal, activating a magical McGuffin, getting run over by Truck-kun and reincarnated (Tensei in weeb, a genre isekai ate), being summoned by the denizens of the world, or the ever-popular getting your brain downloaded into your favorite MMORPG.

The term (and to a lesser extent the genre) have been kicking around the weeaboosphere for a while, but around 2015 publishers started flooding the market with insufferably awful series (with insufferably long titles) that sell both in Japan and internationally like hotcakes, no matter how bland and generic they get. This once again proves that no matter which side of the planet you're on, otaku are autistic retards with no taste. As of 2018 this seems to be tapering off; Kadokawa has banned isekai stories from their light novel competitions, and fewer and fewer isekai light novels get adapted into anime each season, and parodies are becoming more and more common, leaving it only a matter of time before the genre hits "even the parodies are stale" levels of played out.

Why do people hate it so much?

As noted below, stories of people entering other worlds are nothing new, and speaks to a common desire to experience strange and exotic lands. Yet Isekai stories still get a lot of flak for many reasons. Besides there being way too many anime/manga that are all basically the same story with slightly different premises, it boils down to a number of common gripes:

• The biggest one is that rather than trying to tell a compelling and interesting story, too many Isekai stories are just the basest wish fulfillment fantasies for the lonely basement-dwelling neckbeard. Most of the other complaints are derived from this one.
• The hallmark of isekai stories is defining of the world in terms of RPG mechanics. People in isekai worlds speak of levels, classes, and experience as real and tangible things as opposed to the mechanical abstractions fa/tg/uys normally recognize them as. Outside of Isekai stories that actually take place inside of RPGs or videogame RPGs, this is pretty much inexcusable.
• Isekai protagonists tend to be big fucking nerds who immediately recognize what's all about and exploit it, often aided by unreasonably high stats relative to their abilities in real life. The unstated implication is that the overweight slimeball watching/reading the isekai story would be just as successful as the protagonist because of his valuable and hard-earned RPG knowledge.
• The protagonist frequently is overpowered in a way that puts him way ahead of his peers, despite lacking any useful combat, intellectual, or even social skills from his homeworld. Rarely does the protagonist have to put that much effort in overcoming his obstacles.
• Even more offensive protagonists will be actively unlikable or even outright repulsive, despite not suffering any consequences for it.
• And on top of that, 99.9% of the time, the protaganist has an all-female harem party who hang on his every word. Is this starting to sound familiar?
• For more Isekai-specific gripes, while many stories are just copycats of one another, some will attempt to put an "original spin" on the genre, usually by adding a gimmick. If done well, then the story still has some value in being interesting and explore otherwise ignored facets of an overused genre. Done poorly, and it comes across as just plain tiresome, especially if the gimmick is the only thing keeping the story afloat when the characters and plot fail to impress.
• Almost all the protagonists in isekai stories have tragic background. Not saying that this is a bad thing, but it is almost as if the author is trying to push the bill, forcing the reader to go through 1 or 2 chapters of flash backs. This gets worse when they are all generic manga cliches. But some tragic backgrounds are so well detailed it's almost as if the author self inserted their past there. Here is a few examples:
  • Daddy/Mommy issues - According to various manga, Japanese parents are some of the worst in all of Asia since their working conditions over there have a very high demand and busy schedule that the parents are too busy at work to spend any time with their children (a situation that is a genuine issue, but not something the MC bothers with explaining). Other than that, the parents can be highly demanding, overfocusing on academic performance at the cost of any other development in that edgy way that teenagers rebel against mom & dad. Sometimes, parents can also be drunken scumbags who either abandon their children of the next high or just straight up mistreat them. Protagonists with tragic background like these often has low self-esteem and edginess but have it all fixed up in the other world since now they are popular with bitches.
  • School problems - Way too many isekai protagonists have school-centric tragic backgrounds where they are either bullied in school or have no friends. Probably that's why they become nerds and are able to develop their very own hobbies alone, which just happen to be the cheat key in the other world.
  • NEET - Oh baby, don't even get me started. NEET is an acronym for "Not in Education, Employment, or Training," typically including basement-dwelling adult virgins, unemployed nerds who live alone which makes them the definition of a loser. It is no surprise such a failure could gets cheat powers in the other world compared how piss poor they did in real life.
• O MY GLORIOUS NIPPON STEEL FOLDED OVER 9000 TIMES. Basically just to show how superior the Japanese are compared to the other world. GATE is the worst example of this where the Japanese military in the other world id wrecking havoc with their modern weaponry (keep in mind real life modern Japan don't have their own army, but a self-defense force that cannot be compared to the actual military might like American or Chinese military, no offense). Other than that, various Japanese food and their favorite katana blade are also introduced in the other world to prove their superiority. It's almost if these mass produced Isekai stories and manga are just to advertise Japan's superiority to compensate for something...
• The worlds traveled to are usually bland and unoriginal; usually, it's just the JRPG version of the standard fantasy setting, with actual in-universe RPG mechanics. The distancing effect of the latter is rather bad, and the oversaturation of the former only makes things worse.

Isekai and /tg/

Although most isekai stories get panned on /tg/ for annoying meta-humor, generic shonen bullshit, generic fanservice bullshit, or a combination thereof (if not the characters being blatantly Mary Sues, or presenting something even more absurd), a handful of series are decent enough to merit genuine approval. Or they're tolerated because they have monstergirls. Check our anime and manga pages for the current scoop.

While isekai is a distinctly Japanese form of cancer, the basic idea of people from our world getting chucked into a fantastic world and forced to fend for themselves is practically universal and turns up moderately often in Western fantasy with the earliest example perhaps being "A Connecticut Yankee in King Arthur's Court" by Mark Twain which was published in 1889. Oddly, when this happens it tends to be rather less shit perhaps due to it being less common. L. Frank Baum's Oz series, Alice's Adventures in Wonderland by Lewis Carroll, and Edgar Rice Burroughs' Barsoom novels are iconic examples of the core premise that predate cliche fantasy, and C.S. Lewis The Chronicles of Narnia uses the plot for Christian allegory. The NeverEnding Story is the flagship modern western example, and right in the heart of the fantasy cliche storm; Yet it is the purest anti-shit, either despite or because of this. Or at least, it avoids being the self-indulgent wish-fulfillment for irredeemably unlikable losers that makes Isekai so widely hated. One could make the case that The Matrix is an isekai story (it basically reverses a couple of the key tropes), though classifying it as "less shit" may not be accurate for some people. A /tg/ example that (in hindsight anyway) fits the isekai mold well is GURPS' flagship fantasy setting, which revolves around people from across the universe getting isekai'd to the planet of Yrth by an extradimensional "Banestorm" and proposes that players could stat themselves and then play as themselves on Yrth after getting deposited there by the Banestorm.

Isekai also has its influence on Old School Roleplaying; as stated above, there are plenty of pulp fantasy novels involving ordinary souls getting sucked into a strange, alien world and becoming heroic adventurers as a result. Hell, Greyhawk has several deities who actually originated on other worlds - Murlynd, Saint Cuthbert and Mayaheine‎‎ have all been implied to have come to Oerth from "real" Earth - whilst the Forgotten Realms was, once upon a time, hinted as being connected to Earth by various portals to different times and places; the not!Egyptian race was actually supposed to be peopled by real ancient Egyptians who had been summoned to the Realms en-masse by evil sorcerers as slave labor, only to break free of them. Then there's the D&D Cartoon, whose plot was D&D by way of Isekai. That being said, unless your DM was being really lazy, if you tried to talk in-universe about stats or levels or other meta game content like they do in Isekai stories, NPCs would and should treat you like a madman.

Reverse Isekai

Occasionally, reverse isekai plots, where supernatural elements from other dimensions have invaded the "real" world, have appeared in /tg/. D20 Modern's default for supernatural entities is that they a dropped onto Earth from another plane, "The Shadow", and can't go home (though their corpses vanish upon death). The Adventure Path Reign of Winter has a trip to World War I era Russia where the party fights Mosin-Nagants and machine gun wielding Russian soldiers, tear gas elementals and actual Grigori Rasputin.

One odd feature in Japanese Reverse-Isekais is an emphasis on how Japanese food is so much more awesome than whatever bland, flavorless food the peasants of the fantasy world have to eat. In fact, there actually is more than one anime about people from a fantasy world visiting a restaurant in modern Japan. Which in fairness: the modern world wide food distribution networks that can ship sun ripened lemons and meat to any point in the world within 24 hours is likely going to compare favorable to all but the highest fantasy fare. Even so, even the lowliest peasant would put some effort in using what they had to make food taste good; even if they couldn't afford spices, herbs were still easy enough to get a hold of, and rural cooks knew enough about how to prepare meats to make them taste good. Whereas fantasy peasants may as well be eating dry, stringy meat with a side of boiled, unseasoned vegetables and mud for dessert.

List of Isekai

Note: This list currently focuses on mainly isekai that started as an anime or have had an anime adaption. There is a huge number of isekai manga, web novels, and light novels that have yet to have an anime adaption, which for many of them is a good thing.

Good Ones

• Aura Battler Dunbine: The first classic, pre-SAO isekai anime, or at least the earliest one worth remembering, which at its most basic can be described as Isekai Fantasy Gundam (apt, considering that both were made by the same guy). Sho Zama, a dissatisfied japanese youth about to get himself killed in reckless motorcycle stunt on a busy highway, is suddenly summoned into an alternate medieval fantasy world, Byston Well, where a local duke by the name of Drake Luft forcibly recruits him and other summoned into his army. Drake Luft was gradually jumpstarting an industrial revolution with a help from other "Upper Earthers" he summoned via a captive fey to give him an edge in his plans to conquer Byston Well while he holds the first adopter advantage, and one of these advantages are the titular mechas, the Aura Battlers which are powered and enhanced by the pilot's Aura (which the summoned Upper Earthers have more powerful ones compared to the locals) with one called Dunbine to be piloted by Sho, who later steals it to join the resistance. The show can be divided into two halves: The first with gradual escalation from guerilla warfare with medieval weaponry supported by Aura Machines to open warfare between kingdoms fielding 100% Aura Machine Armies led by huge Battlecarriers, while the second half starts with the Fey Queen deciding that all Aura Machines were evil and at a cost of her life chucks them all, pilots and armies included, back to Upper Earth, which is in the middle of Cold War.
• Overlord: A gamer gets trapped in the body of his max level Lich avatar and sent to another world, bringing with him all of his treasures and minions (who now are real people) and guild base. He even has a shitton of cash shop items that he pulls out once in a while during the few encounters that his OP powers aren't enough. He starts out trying to be a good guy in the new world, but he ends up turning into a villain on a path to conquer the new world due to a combination of losing a lot of his ability to feel emotions and his minions expecting him to play the role of a villain.
• That Time I Got Reincarnated as a Slime: A man dies an wakes up in the body of a super powerful Slime creature with the ability to copy the powers of whatever they eat. They end up becoming the chief of a goblin village and expanding it into a new nation. Something interesting about this series is that it plays with the idea of how most monsters in games are just nameless mooks and only named monsters are an actual threat; here, nearly all monsters are born without a name, but a more powerful entity (usually a demon, or in our slime's case, his elder dragon BFF) can lend a monster some of their power simply by naming them. The protagonist abuses the shit out of this and names every monster tribe in his confederation, giving them all a newfound sense of purpose and identity along with it. While being on good terms with the human & dwarf nations, the demon-controlled nations are not too happy about this upstart slime and scheme to bring him down.
• Kiba: What happens when you combine Pokémon with Game of Thrones and a bit of 1985, and then give everyone lightsabers. An obscure but definitely worth watching show about two friends who separately end up in another world where some people have the ability to pull marble like objects out of one part of their body which are used to cast spells, power up lightsaber like weapons, and summon powerful monsters called spirits. Each of them ends up possessing one of the six most powerful spirits in the world which the nations of the new world are fighting for control of. The first boy ends up in the only truly nice nation, while the other ends up in a country that at first seems nice but turns out to be a horrible dystopia where the population is so brainwashed that they are willing to accept capital punishment with a smile for minor crimes even if they committed them accident.
• MÄR: A boy named Ginta gets summoned to another world populated by people based on characters from fairytales and popular classic fantasy books who fight using magical items called ÄRMs. He gets a hold of an intelligent ÄRM named Babbo who can turn into anything he can image. He and several characters including Dorothy from The Wizard of Oz and Jack from Jack and the Beanstalk team up for a tournament to decide the fate of the world against a villainous organization called the Chess Pieces.
• Do You Love Your Mom and Her Two-Hit Multi-Target Attacks?: A parody of typical trapped in a video game wish fulfillment stories. A boy's wish to go into a video game is granted, but his dream is ruined because he is forced to bring his extremely attractive and clingy mother with him, who is a lot more powerful than him in the game world. The show also parodies the incest themes popular in a lot of recent anime and light novels, as the main character finds his own mother attractive but is entirely disgusted by those feelings and his mom is too oblivious to realize how uncomfortable her age-inappropriate behavior makes him, and her feeling her him really aren't sexual at all.
• Spirited Away: A girl and her parents accidentally wander into the world of spirits and the parents get turned into pigs by a witch as punishment for stealing food. With the help of a mysterious boy who can turn into a dragon, she gets herself a job working for the witch at her bathhouse for spirits until she can find a way to set her parents free. This one is by Hayao Miyazaki and has all of the Studio Ghibli flare that weebs constantly point to to say that anime is more than just stupid cartoons.
• Those Who Hunt Elves: A comedy about a group of people are summoned to another world and can't go back until they can find 5 tattoos placed on 5 random elves somewhere in the world. To find them they strip every elf they meet naked.
• Youjo Senki: Saga of Tanya the Evil: A sociopathic atheist is murdered by somebody he sacked because corporatism, and meets a being who claims to be God. He refuses to believe it really is God (And instead labels 'Being X', sort of like how Star Trek treats a number of hyper-advanced races with god-like powers) and as punishment gets reincarnated as a female child solider in a world resembling WWI Europe, only with magic. Said female child ends up duckfacing her way up the ranks of not!Germany and acquiring a number of orbiters who either fear or respect. Her main problem is that she keeps getting posted to incredibly dangerous missions despite desperately wanting nothing more than a desk job away from the front lines so as not to die again and face Being X or his lackeys (all other deities from other faiths).
• Drifters: Written and drawn by the author of HELLSING. This is a story about fighting against fate where historic heroes, wise men and generals from the real world (mostly those who get ambiguous or "missing in action/no body was found" ends) are intercepted at the point where they should have died by rather mundane looking-but-apparently divine office worker named Murasaki, and given a choice: to either meet their fates and die, or to live on but get transported to another world -- one that happens to be in the middle of a massive fight for survival. Needless to say many choose the latter, including the main viewpoint character, Shimazu Toyohisa of the Shimazu clan. Called Drifters, this group includes of historical badasses (including Oda Nobunaga, Butch Cassidy, Abe no Senmei, Scipio Africanus and Hannibal Barca), he whips up an alliance made up of demihumans and other peoples into a force that might be able to stand up to the force that's threatening to overwhelm the "civilized" peoples: the forces of the Ends. Unlike the Drifters, these are people who in the real world had unambiguously nasty ends -- like Joan of Arc, Rasputin, and Anastasia Romanov -- and are given nasty powers as a result. Led by someone implied to be Joshua bar Joseph (aka Jesus Christ), the Ends want to wipe the slate clean, and give leaving the so-called monstrous races (Orcs, Goblins, etc.) to inherit the world. Compared to other Isekai, the series is themed around second chances (aka don't die the same way as they did before) and was heavily reinforced in the first encountered with the black king. By the way, this series is being slowly released and is on multiple hiatus for unknown reason since it is kind of a trait now days for good mangaka to fucking around their job.
• Konosuba: A comedy series, and one of the first to take the piss out of the Isekai genre. It begins with a NEET shut-in dying to save a girl from being hit by a truck, whereupon he's met by a goddess in the afterlife. She reveals that the girl was actually not in danger (it was actually a tractor moving at around 2 miles an hour) and he died of a heart attack, followed by pissing himself, which she mocks him relentlessly over. She then offers him to reincarnate in another world and defeat the devil king, and in return he can have any powerful item he wants. Out of revenge for her mocking him, he picks her and the two end up trapped in a fantasy world. The goddess turns out to be pretty damn useless 90% of the time and a huge bitch, and later they are joined by two other girls (a bratty pyromaniac wizard loli who can only cast one spell a day, and a masochistic knight who can't hit anything for shit and makes both enemies and allies alike uncomfortable) to form one of the most dysfunctional parties in existence. It manages to be both a clever deconstruction of isekai and a pretty hilarious fantasy-themed sitcom all at once.
• Escaflowne: A Japanese high school girl is teleported to a magical world (one that can see the Earth but Earth can't see it due to magical stuff or something) where the weapon of choice are "Guymelefs"; magitek mecha that resemble fantastical giant knights powered by the crystalline hearts of dragons. She gets caught up in a whole slew of crazy as the evil empire shows up and starts conquering the world while the male lead, the heir to one of the conquered kingdoms, and a ragtag group of rebels struggle to overthrow the empire and restore things to a semblance of normalcy. Had a very pretty anime movie made of it but the movie mashed a lot of plot elements and characters together while also cutting a huge chunk of the story as well.
• Inuyasha: A rarity in that the teleported protagonist is female, and travel between the fantasy world and the real world happens frequently. Ordinary school-girl Kagome Higurashi learns that her crazy grampa's ramblings about the ancient well in the shrine her family lives at really is magical when a many-armed big-tittied centipede woman pulls her into the well and transports her into Feudal Japan, ranting about killing her and taking a magical "Shikon Jewel" that can make demons into gods. To not be killed, she reluctantly releases Inuyasha; a bad-tempered half-inugami (dog demon) who looks like a bishie boy with long, flowing white hair, claws, and a pair of cute dog-like ears. During the struggle, the Shikon Jewel is shattered, forcing her to reluctantly team up with Inuyasha (who used to be in love with her previous incarnation, the shrine maiden Kikyo) to track down the shards before they can wreak havoc across the land. Their party grows to incorporate Shippo (a baby kitsune boy), Sango (a badass warrior-woman who uses a giant boomerang made of demon bones), and Miroku (a perverted but handsome young monk who sports a miniature black-hole in his right hand... that will ultimately devour him whole, as it has his entire family), and their mission expands to tracking down and destroying Naraku; a bandit turned Demon Prince who has his own evil plans for the Shikon Jewel and who was responsible for the misery that befell Inuyasha and Kikyo.
• Rising of the Shield Hero: Four heroes are summoned to another world that partially runs on RPG rules (it has classes, levels, and experience, but some of the heroes make mistakes based on expecting the world to work like an RPG in places where it doesn't) to defend it against a phenomenon called the Waves of Catastrophe, where the sky turns red and armies of monsters appear. Each of them is assigned a powerful holy weapon (sword, spear, bow, and shield) and forms their own party to help them level up. However, the hero assigned to the shield immediately gets robbed and falsely accused of attempted rape by his only party member, who seemingly did it just so they could give his stuff to the spear hero as a present. With that horrible start, the shield hero loses interest in saving the world and only cares about going home or getting revenge. To survive, he is forced to build up his reputation, wealth, and power from nothing while all of the other heroes (who turn out to be all be idiots) soar ahead of him. And since nobody wants to ally with him and his shield keeps him from wielding any other weapons, he forced to buy a Monstergirl slave to help him fight and builds himself up as a hero for the common man rather than the uncaring and snobbish elite. On a side note, when it first came out, SJWs threw an absolute hissy fit over how "problematic" they perceived this show to be. So take that as a glowing recommendation.
• .hack: One of the earliest isekai to make big waves in the US, .hack is a franchise made up of several anime, manga lines and video games that take place in the near future (at the time they started, the year chose being 2009) where VR video games are not only wildly popular but one (simply called "The World") is the most popular game in existence. People the world over play the game and form guilds and play together. The main character from .hack//Sign, Tsukasa, does not want to play with others though due to some deep-seated weirdness and quickly find out that they cannot log out of the game. Oh, and some weird floating slime monster attacks and kills other player's avatars, those so attacked fall into comas in the real world. And there is some sort of floating loli that Tsukasa communicates with as well. Fairly quickly a group of people begin to hunt Tsukasa while another group tries to helm him (later to find out "he" is actually a "she"). Series ends kind of meh but kicked off a major franchise that then pretty collapsed under its own weight (multiple games within a handful of years, multiple manga stories, spin-off anime and more that, in the end, couldn't pay for themselves).
• Log Horizon: A new update of old-school PC MMORPG Elder Tale ends up dragging its entire logged-in player base into the world it portrayed. Veteran player Shiroe and a few of his friends try to figure out what to do with their new existence, before finally deciding to take an active stance in influencing their current reality for the better. This, on top on trying to find out just WHY everyone got dragged into Elder Tale, or at the very least, a world that seems to look like the game world.
• Re:Zero:

Bad Ones

• Sword Art Online: One of shows responsible for the explosion in the popularity of Isekai. Was very popular when it came out, but as Reki Kawahara continued the series: the quality of the story degraded slowly over the years, and along with it the general fanbase's opinion. It still has it's fans, along with a sizable amount of detractors (as most feel SAO's popularity is undeserved, and taking the spotlight off other shows worth the praise, or because its just popular). The initial premise of SAO is that true VR is achieved through a VR helmet called the "NerveGear", which transports the mind of the wearer into virtual space in a process called "Full Dive". However, Akihiko Kayaba, the inventor of the device sabotaged it and instead: traps everyone in SAO by removing the log-out feature, and secretly installed a kill-switch onto the helmets that will fry the user's brain if they forcefully yank out the helmet or they run out of HP in the game. The only way to log out is to clear a tower-like dungeon in the middle of the game, which is filled with high-level mobs and boss-creatures, so the trapped players band together to clear the tower and get out, while some just fuck around and exploit the situation to their benefit. The plot itself has interesting ideas on how teens and young adults cope with the threat of actual death while in a video game (or wanton disregard for it), but has plenty of glossed-over plot holes at the same time, that if you look too far into it: makes the entire story nonsensical (such as factoring human physiology into account: most people inside SAO would have died in less than a week due to IRL malnutrition). It also doesn’t help that the protagonist, Kirito, is an unabashed edgy Marty Sue (although the edgy part eventually mellows down, he's still a Marty Sue in all depictions. On a side note, Kirito is also responsible for the painful influx of terribly written edgy teenage dual sword-wielding OCs in the early 2010s, to the point there's now a slight stigma with using dual-swords for your character in RPGs) and the first season ended on a nonsensical conclusion. The female characters that make up Kirito's not-harem are waifu material though, if that's any consolation, and SAO at the very least has the decency to write them as their own relatable characters, instead of being orbiting cumdumpsters for the protag to cockblock at will (and as bad as his character is written, Kirito still has a wholesome relationship with his in-game waifu, turned IRL waifu Asuna.).
• GATE: Thus the JSDF Went There: This was a series that had some potential as the premise was somewhat similar to Stargate; A gateway to another world suddenly appears right in the middle of Tokyo, and almost immediately a bunch of monsters and medieval soldiers start pouring out and attacking anyone in sight. Naturally, the modern Japanese military beats them back, then decides to invade the other world to hold those responsible for the attack accountable. This could've been a good story as there's some actual political intrigue on both sides of the gate, but besides the usual Isekai problems (The protagonist is a lazy underachiever and yet has specops credentials, and has a harem of girls who are or look half his age) its also in-your-face nationalistic, to the point where the Japanese Self-Defense Force effortlessly curbstomps any enemy they go up against, including three different spy agencies and the capital of the enemy empire. Besides removing any tension from the story, its also pretty much transparent pro-military propaganda, where all of the military's more pacifistic political opponents are portrayed as self-centered opportunists. Nevermind that the JSDF basically claimed the other world as their sovereign territory by virtue of being connected to Japan and are seeking to exploit its resources. This should set off alarm bells for those of you who know history.
• In Another World With My Smartphone: The protag gets accidentally offed by God, and as an apology resurrects him with god-tier stats and a smartphone with several, mostly unfair features. He is, without a doubt, the most unironically-blatant Marty Sue to grace recent times. Also its a romance-less harem animu on the side, they're not even trying to aim above the 13-year old demographic.
• The Master of Ragnarok & Blesser of Einherjar: Even worse than Smartphone. Possibly the worst isakai ever. Take everything people hate about isekai and turn it up to eleven. Lazy animation, a harem that includes disturbingly young girls, and an unwatchably boring plot. Also has a guy with a smartphone, oddly enough.
• Garzey's Wing: 1996 release, widely hailed as one of the worst anime ever made; particularly, the Central Park Media dub made an already incoherent plot even more nonsensical. For example, one notorious line goes "We have to circle quickly. We need a stirrup to do this. But don't be unduly concerned. We can use our spears to stand our ground firmly."
• [New Life+] Young Again in Another World: This is just another generic isekai about a MC that was killed and sent to another world by God. But what's so bad about this one that it deserves to be mentioned here? Well, it turns out the MC of this one in life was a soldier who participated the Second Sino-Japanese War in China where he used his GLORIOUS KATANA FOLDED 9000 TIMES and killed over 3000+ people. You still with me? Good. After the anime was announced, controversy obviously started and China threw its weight around and forced the publishing company to not only cancel the anime, but canned the publishing of the novels as well. Every shipment about this piece of trash was stopped. To make matter worse, many anons also found old tweets from the author on Twitter made before the first volume of his isekai was published, where he demeans both Chinese and Koreans, calling them inhuman and lacking morality. These incidents have proven that a good chunk of Japanese isekai authors not only suck in writing, but can be some of the worst scumbags in Japan as well as the overall world.

Weird Ones

Or at least the tolerably weird ones, or those otherwise of some significance.

• Isekai Quartet: Take the main casts of "Overlord", "Konosuba", "Saga of Tanya" and "Re: Zero" find themselves in a middle school. Most of them want to return "home". The result? A somewhat interesting gag series about an Isekai squared situation. Weird because it blurs the line between Isekai, Reverse Isekai, and Not Isekai. Funny, but only if you have some awareness of at least one (and preferably more) of the four series, and are willing to tolerate "HILARITY ENSUES" grade "hi-jinks".
• Restaurant to Another World: One of the few Reverse Isekai stories. There's no overarching plot or villains, just a bunch of fantasy folk visiting a restaurant in Japan. Each patron has their own quirks and favorite dish, as well as their story of how they came to discover the restaurant and the friends they make inside.
• Plus-Sized Elf: Another reverse Isekai featuring a cast of Monstergirls in Japan who can't return home because they all got fat from eating too much delicious but unhealthy food. They're being helped by a health and fitness expert to lose weight, but each girl's obsessions and constant infighting keeps them from making too much progress. The manga has some actual fitness tips sprinkled throughout, but it's also pretty lewd at times.
• Kyoryu Wakusei　(Dinosaur Planet): A fairly old (1993) blend of live action (for the "real world" parts) and anime (for the virtual parts) for kids. The adventures of a girl in a (highly inaccurate) virtual simulation of dinosaur times with her navigator in the real world. Strangely contains a fanservice scene of the girl's virtual avatar (who admittedly looks nothing like her real self, with different hair style and color plus a different actor). The reason this even mentioned is it's one of the primary theories of where the hell the term 萌 (Moe) comes from: The girl's avatar is named that (and, unlike the other major theory, Hotaru Tomoe of Sailor Moon, uses the same kanji) and said fanservice scene greeted with a very enthusiastic statement of "萌～...".
• Thermae Romae: A comedy about a Roman Thermae architect accidentally traveled to modern Japan after he slipped into Thermae bath water. There, he learned a great deal of knowledge about the flat-face (how he calls the Japanese) and using these knowledge to improve Roman Thermae when he got back. Later chapters turns into time traveler's wife where he met this Roman culture obsessed Japanese girl (and the only "flat-face" he could communicate in latin btw) and fall in love with her.