What is isekai?

Isekai (異世界), whose literal translation from Japanese is "another world", is known today as a subgenre, although many already consider it practically a full-fledged genre. It is where the protagonist is summoned, reincarnated, or transported to another fantasy world, either with a specific purpose or due to some error of fate and the plot.

However, something that heavily characterizes Isekai is that in the vast majority of current stories, the protagonist usually has unparalleled powers. Something akin to being "overpowered" (OP) from the start. Their "hero's journey" usually either takes a gigantic leap at some point in the story or simply revolves around going from the worst to the best. A plot device that the first stories of this type managed to adapt and were interesting, but which has become worn out over time.

What was the First Isekai?

The first Isekai, strange as it may seem, is not recent by any means; it dates back to the 80s, with an anime called Aura Battler Dunbine in 1983. This is considered by many to be the first Isekai because it meets a key premise: the protagonist is transported or transmigrated, as you prefer to call it, from modern Japan to a fantasy realm. Something that undoubtedly gives this work the title of the first Isekai.

However, despite being the first Isekai in the 80s, Aura Battler Dunbine was not actually considered an Isekai back then. It was more of a mecha anime, as Isekai truly gained popularity around 2010. This was the era when we were flooded with Isekai everywhere, and it was when its ascent truly began to the point of almost being a genre today.

Isekai Subgenres

Yes, you heard that right, Isekai is not yet formally considered a genre, but it already has a plethora of associated subgenres, among which these three stand out:

1. Summoning Isekai

This is where the classic "I was summoned to another world" title that Isekai often use comes into play. Despite being the most used and "classic," it is the most popular, as the protagonist's summoning always comes with some "power" they did not have in their previous world. They usually have a defined purpose, such as "Defeat the Demon King" or "Save the world from [Insert generic evil name]".

In simple terms, the protagonist is summoned with powers that make them unstoppable. Some of the most popular examples we could mention are:

1. The Rising of the Shield Hero (Tate no Yūsha no Nariagari)
2. No Game No Life
3. The Familiar of Zero (Zero no Tsukaima)
4. KonoSuba: God's Blessing on This Wonderful World! (Kono Subarashii Sekai ni Shukufuku o!)
5. How Not to Summon a Demon Lord (Isekai Maō to Shōkan Shōjo no Dorei Majutsu)

2. Reincarnation Isekai

Reincarnation is another well-known Isekai plot device; it's basically retaining our memories and going to another life in a different world. But something that made it very popular is that retaining "modern" world memories often brings many advantages in medieval fantasy settings. However, nobody said you must always reincarnate as a human. In many anime, to give it a much more fantastical and "different" twist, we have reincarnations into all sorts of creatures or even objects. Such is the case of Rimuru in That Time I Got Reincarnated as a Slime (Tensei Shitara Slime Datta Ken) or more extreme cases like Reborn as a Vending Machine, I Now Wander the Dungeon (Jidōhanbaiki ni Umarekawatta Ore wa Meikyū o Samayō).

Some of the most popular in this Isekai subgenre are:

1. Mushoku Tensei: Jobless Reincarnation
2. That Time I Got Reincarnated as a Slime
3. Ascendance of a Bookworm
4. So I'm a Spider, So What? (Kumo desu ga, Nani ka?)
5. The Eminence in Shadow (Kage no Jitsuryokusha ni Naritakute!)

3. Transportation Isekai (Without Summoning)

This type of Isekai is where the protagonist goes to another world but without being summoned or being sent by some "god" with a mission. These are often virtual worlds where the protagonist is either trapped or simply transitions to them very smoothly. Among these, we have popular ones like Sword Art Online and Overlord; in both cases, they are video games that became their "realities." Although SAO is harder to classify because they enter and exit the virtual world, so we could say that Log Horizon is easier to place in this category.

Some of the most popular in the Transportation Isekai subgenre (Without Summoning) would be:

1. Log Horizon
2. Overlord
3. Grimgar of Fantasy and Ash (Hai to Gensou no Grimgar)
4. .hack//Sign
5. Sword Art Online

Isekai and Their Absurd Power Levels

The "overpowered" (OP) protagonists of Isekai have shifted from focusing on the struggle to acquire strength or overcome existential challenges to the modern Isekai, which tends to focus on how the already invincible protagonist interacts with the new world and the consequences of their absolute power. This approach seems to reflect a trend in Japanese web literature, where authors must quickly attract a large audience with the promise of instant gratification through powerful heroes who can sweep everything in their path.