Isekai (Japanese: 異世界) (lit. "different world") is a subgenre of Japanese fantasy light novels, manga, anime, and video games revolving around a normal person being transported to or trapped in a parallel universe. Often, this universe already exists in the protagonist's world as a fictional universe, but it may also be unknown to them.
The subgenre can be characterized as wish fulfillment, with the person being transported often being a NEET, hikikomori, or gamer. In the new fantasy world, they are able to succeed through use of their comparatively unimportant-in-real-life genre knowledge, or gaming skills through the use of a game interface only they can access.