This is the story of Ketil Bane Greenfield, son of a Dryad named Kanon Greenfield and an isekai men who comes from Japan, his name is Hiroki Satō, but in that world they know him as Galion Bane, the greatest hero the world has ever seen. Galion after achieving everything he wanted in this world, decided to artificially sire an heir so he can defend the Greenfield forest, now that Galion denies his immortality and passes away, the world needs a new hero before he destroys himself.