This plot device emphasizes worldbuilding and non-protagonist characters, and typically allows the audience to learn about the new world at the same pace as the protagonist over the course of their quest or lifetime.
However, the first modern isekai works were Haruka Takachiho's novel Warrior from Another World and Yoshiyuki Tomino's television series Aura Battler Dunbine.
The concept of isekai has antecedents in ancient Japanese literature, particularly the story of a fisherman Urashima Tarō, who saves a turtle and is brought to a wondrous undersea kingdom.
Other precursors to isekai include portal fantasy stories from English literature, notably the novels Alice's Adventures in Wonderland (1865), A Connecticut Yankee in King Arthur's Court (1889), The Wonderful Wizard of Oz (1900), Peter Pan (1904), and The Chronicles of Narnia (1950).
[2][3][4] The earliest isekai anime to involve the protagonist being trapped in the virtual world of a video game was the film Super Mario Bros.: The Great Mission to Rescue Princess Peach!
The Familiar of Zero fan fiction writers eventually began writing original isekai novels, such as Tappei Nagatsuki who went on to create Re:Zero (2012 debut).
[19] In Sorcerous Stabber Orphen, an entire population of humans appear in the magically created world, transported from Earth, and are partially mixed with local dragonlike Heavenly Beings.
[20] In many works, isekai overlaps with the harem and LitRPG genres, where the protagonist gains the affection of several potential love interests, who may or may not be human.
The protagonist is reborn in a new world, but their appearances and personalities are not altered in any way; however, they are still given special powers as well as a magical object that aids them on their journey.
These stories follow the main character’s journey of avoiding the grim, predestined "Bad End" fate of an otome villainess.
Isekai villainess anime feature the contrary, pinning characters in a doom-ridden role and denying them any sort of free will within the game.
With most characters working against the "Villainess", the protagonist granted more agency and moral grayness than a normal "Heroine", being is thrown in a race against time to avoid the game's predestined fate.
[19] The isekai genre became so popular during the early- and mid-2010s that it started to generate backlash, both in Japan and overseas, from those who felt that it was overcrowding the greater manga and anime market.
In 2016, a Japanese short story contest organized by Bungaku Free Market and Shōsetsuka ni Narō placed a blanket ban on any entries involving isekai.