The Japanese anime industry has invented a few subgenres of its own, including the ever-popular isekai subgenre. In broad terms, isekai is all about an ordinary, real-life person finding themselves in a brand-new world to explore, like the anime version of The Wizard of Oz or The Chronicles of Narnia. Isekai, despite being notoriously formulaic and predictable, has become hugely popular, especially when reincarnation is involved.
Source：https://www.cbr.com/reincarnation-isekai-anime-popularity-explained/
