Kamitachi ni Hirowareta Otoko Manga

After dying at 39, an overworked man named Ryouma Takuma is sent by the gods to a world where magic exists. He begins a new life there as a boy, carrying the experiences of his previous life and abilities granted to him by the gods. Awakening in a forest, Ryouma discovers that he can tame monsters, especially slimes. With his slime companions, he adjusts to life in this unfamiliar world, explores his abilities, and learns that slimes have more to them than first appears.