Dorei Kara no Kitai to Hyouka no Sei de Sakushu Dekinai no da ga

A reincarnated boy, Allen, gets bequeathed by a goddess the cheat skill, "Restoration." Even though he can heal all and any injuries and illnesses, there aren't a lot of places where he can use that skill to the fullest, so he planned to "regenerate" the slaves he bought and lead a slow-paced life.