ウチの使い魔がすみません

In this world, Makai, every Demon gets a Familiar summoned using their magic. Patty, a Demon Girl who's magic is so weak she can't even summon an animal is forced to get a famliar. So, reluctantly, she chooses an older human named Norman as her familiar. Norman has an incredible fascination with examining all types of lifeforms around Makai, claiming he loves learning about them. This weird combination of a weak demon girl and a goofy old man leads to a journey of adventures the two go through.