Genres
Isekai
Fiction in which an ordinary Earth protagonist is transported, reincarnated or summoned into a parallel world.
Isekai is fiction in which an ordinary Earth protagonist is transported, reincarnated or summoned into a parallel world. The crossing itself is the obligatory beat. Recurring setup elements: a transportation event (death via truck-kun, a portal, a summoning), RPG-like powers gained on arrival, little drive to return home, and accumulating companions.
"Narou-style" isekai, from the Japanese web-fiction site Shosetsuka ni Naro, is a real named subgenre; in that style, harem elements are described as having become part of the standard formula. Isekai is closely related to the older Western tradition of portal fantasy; genre references treat them as overlapping traditions rather than parent and subgenre.
See how to write isekai.