The Manga was about a world that has special pets. Example - The Demon lord, the Hero, and ext. This boy who got lucky and found the demon lord now has him as a pet, there's no conflict and War is just a normal world that has these type of pets and who live in your normal family. The story is mainly about the adventures they have with each other and funny moments in which they share together.
Uchi no Maou Kamimasen yo