Maou no Musume wa Yasashisugiru!!

Demon King Ahriman is ready to conquer the world until he encounters an enemy he has no idea how to defeat: his daughter Doux is simply too kind. Instead of frightening humans, she befriends them, and instead of spreading misery, she helps anyone in need, making even the demons' enemies struggle to dislike her. Ahriman orders his aide Jahi to train Doux into a properly terrifying demon, but every lesson in cruelty somehow becomes another good deed, and the worst part is that her father cannot stop being proud of her.