This is essentially my version the monster girl encyclopedia universe

Meet Y/N Morningstar, the official Prince of Hell son of Lucifer and Lilith, and Charlie Morningstar's younger twin brother. After his mother vanished, Y/N left the palace to start a new life in IMP City. There, he joined I.M.P (Immediate Murder Professionals) as an assassin, working alongside a team of Imps and a hellhound. And this is where his story begins