As he was being destroyed by Son Goku's Spirit Bomb, a piece of Majin Buu would split off into another universe. One of magic and Guilds, where the reborn fragment of the Great Destroyer would be found by a lonely Dragon Slayer and her talking cat.

His rebirth robbing him of his memories, Buu abandoned his past life of violence and mindless destruction. Instead, Majin Buu would be a destroyer of evil and loyal friend to Wendy Marvell. And maybe something else?

(NOTE: NO lemons and NO harems. Buu will be adequately nerfed to make the story fit but will remain quite strong. Don't expect him to steamroll everyone, power-wank is not something I enjoy.)