Isekai

Isekai (異世界) literally means a world apart from the one we live in. In anime and light novels, it most often refers to a genre in which someone from the real world is sent to a fantasy world and has to build a life there.

The setting is usually a medieval-European-style world where swords and magic are abundant. Many of these worlds run on role-playing-game conventions such as levels, skills, and status screens that show a character's abilities as numbers, and the hero works their way up as an adventurer or gets swept into a campaign to defeat the Demon Lord. The stage can also be the inside of a game or a parallel world, so while fantasy is the typical setting, it is not a requirement.

Overseas, the genre is known simply as Isekai. The word was added to the Oxford English Dictionary in 2024, and it has become one of the defining labels for talking about Japanese anime and light novels.

Isekai is a Japanese word that originally just means another world. It is made up of i (異), meaning different, and sekai (世界), meaning world.

Isekai in Fiction

Stories about wandering into another world are nothing new. In Japan too, the setup of a real-world character being whisked away to a different world was already common, as in the 1992 manga Fushigi Yûgi and the novel series The Twelve Kingdoms.

In the summoned form, the 2004 light novel The Familiar of Zero was widely read and helped this type of story multiply.

The Narou-kei Explosion

What really shifted the landscape was a novel-posting site that opened that same year, in 2004, called Shōsetsuka ni Narō (literally, Let's Become a Novelist). Anyone could post and publish fiction for free, and a steady stream of isekai web novels was born there.

Sword Art Online, a huge hit when it was animated in 2012, also pushed the genre into the spotlight. That said, it is a story about being trapped inside an online game rather than moving to live in another world, so some do not count it as isekai in the strict sense. The original author himself has resisted the isekai label.

As works like these spread, the name isekai took hold, and in the English-speaking world the romanized form Isekai became established as well.

Around 2012, hit titles from Narō were adapted into print and anime one after another. They included Mushoku Tensei (Jobless Reincarnation), in which the hero dies and starts life over in another world, That Time I Got Reincarnated as a Slime, where he is reborn as a slime, Re:Zero, which follows a boy thrown into an unfamiliar world, and the comedy-leaning KonoSuba. Most began as web serials around 2012 and 2013. In Japan, works like these are sometimes grouped together as Narou-kei.

As the boom overheated, some began to complain that too many stories shared the same premise. In 2016, a short-story contest co-hosted by the Bungaku Free Market (a literary self-publishing event) and Shōsetsuka ni Narō, and in 2017, a novel contest run by KADOKAWA, both turned away submissions of isekai reincarnation and transportation stories. It was the flip side of the genre becoming a fixture.

Reincarnation, Transportation, and Summoning

There are three broad ways to reach another world. Only the entry point differs, and what happens once the hero arrives is often much the same.

Isekai tensei (reincarnation) is the pattern where the hero dies once in the real world and is reborn in another. They might restart life as a baby, or grow up keeping memories of their past life. Sometimes they are reborn as something other than human, as in That Time I Got Reincarnated as a Slime.

Isekai ten'i (transportation) is the pattern where the hero is sent to another world without dying. One day, out of nowhere, they are standing in an unfamiliar land. Re:Zero is a representative example.

Isekai shōkan (summoning) is the pattern where someone in the other world calls the hero over. Often they are brought in as a hero meant to defeat the Demon Lord. The Familiar of Zero is well known for this.

On fiction-posting websites, however, stories are often categorized into the two types of reincarnation and transportation, with summoning sometimes treated as a subtype of transportation.

Game-like Conventions

Many isekai stories share rules that resemble a role-playing game. There are levels and skills, status screens that show a character's abilities as numbers, adventurer's guilds, and the familiar framework of a Demon Lord and a hero.

The hero is often overwhelmingly strong thanks to a special power they were granted, a so-called cheat ability, and the thrill of crushing enemies with ease has earned this the nickname “ore-TUEEE” (roughly, "I'm SO strong"). Because so much of the template is shared, even first-timers find it easy to grasp the setting of these worlds.

Hit by a Truck Into Another World

A classic isekai-reincarnation opening is for the hero to be struck and killed by a truck, then wake up in another world. It has been used in so many works that overseas fans have turned the truck itself into a running joke, calling it Truck-kun. It has become a fixed device for carrying the hero into the other world, a meme that has come to stand for the genre.

Villainess Stories

A popular form of isekai aimed at girls and women is the subgenre known as villainess stories. The heroine is reincarnated into the world of an otome game, a dating sim made for a female audience, and wakes up as the villainess character from that game. The standard plot has her using the knowledge she gained from the game to dodge the ruin that would otherwise await her.

The best-known example is My Next Life as a Villainess: All Routes Lead to Doom!, nicknamed Hamefura, which became widely known through its 2020 anime adaptation.