The isekai genre of anime is bigger and more popular than ever, and a handful of titles stand out as essential viewing for anyone who wants to get into it. Streaming platforms such as Crunchyroll and Netflix feature all kinds of isekai titles, from the comedy series Konosuba to the action-packed That Time I Got Reincarnated as a Slime. But it all had to start somewhere.
The basic concept goes back much further than that, to the days of The Wizard of Oz and The Chronicles of Narnia, but the modern isekai boom is largely attributed to the popularity of the Sword Art Online franchise, and that raises some questions. Some anime fans credit SAO for launching the isekai trend, while many other fans don't even count SAO as isekai in the first place. The truth is somewhere in the middle.
Sword Art Online, Launching The Isekai Anime Trend
It should be noted that even if a given movie, anime series, comic book or novel launches a trend, that trend might soon deviate from the original work's themes and go in different directions. That appears to be the case for the Sword Art Online franchise, as this anime is credited with popularizing the isekai concept while not firmly establishing -- or following -- all the rules. Ultimately, Sword Art Online is not an isekai anime from a purist standpoint, but it's still easy to see how the franchise got the isekai ball rolling. It has all the ingredients for a popular series: a cool fantasy video game world, a self-insert young male lead with cool swords in his hands, an attractive female love interest who can hold her own and most of all, high stakes in the Aincrad story arc.
Sword Art Online is far from a visionary franchise, and even at the time, it was hardly groundbreaking, following many anime conventions of the era and today alike. Still, it was a cool idea to have thousands of gamers suddenly trapped in an ultra-realistic game world with their lives on the line, and this served as exciting and intriguing escapism for fans of video games and fantasy alike.
Before long, the anime industry started cranking out more and more isekai titles, many of which were based on light novel series published by relatively obscure authors looking to cash in on a trend, generally speaking. The genre quickly mushroomed into what fans know as isekai today, from Dr. Stone to My Next Life as a Villainess and Overlord, among many others. Even if many fans lament the oversaturation of isekai, it's difficult to deny that this genre is hugely popular and has well-established rules for new authors to abide by, and much of that started with Sword Art Online.
Sword Art Online, Abandoned By Its Own Genre
By now, the proliferation of isekai titles makes it easy to establish the core rules of what is and isn't part of the genre, and oddly enough, Sword Online got left behind by its own creation. The series is still popular, of course, but most anime fans don't consider it true isekai, since it doesn't follow the core rules closely enough. An isekai story involves a one-way trip through space and sometimes through time, such as with Dr. Stone or InuYasha, and the protagonist is unlikely to ever return home. In fact, most isekai series involve the protagonist dying first, such as with the infamous "Truck-kun," or a fatal stabbing, which was the case for Rimuru Tempest. Then there's Ainz Ooal Gown, who was locked into his MMORPG game world with no evident way to log out ever again.
By contrast, Sword Art Online involved Kirito and thousands of players fighting to escape the Aincrad world in the game, and from the very start, they had a clear exit, which already puts Sword Art Online's isekai status in doubt. Then, Kirito and his friends started freely logging into and out of game worlds such as ALFheim Online and Gun Gale Online, which is not isekai at all but rather a video game anime. True, Kirito seems totally stuck in the Underworld with Alice and Eugeo, but that's only one story arc of Sword Art Online, not the entire franchise -- and even then, Asuna has hope that she can get Kirito out back into reality.
In short, all this means that Sword Art Online dabbles with isekai elements but only used the isekai concept as one tool of many in its narrative, while true isekai titles, at least in the modern sense, go all in. They are entirely about the one-way trip to another world, and Kirito's journey is anything but that.