Mii

A childish Demon King of an island full of monsters. Kazuto makes her acquaintance while advertising the Dungeon. An optimistic and friendly girl. She wanted to make friends with lots of people, and ended up uniting the island's forces in the process. She becomes fast friends with Kazuto as well.

Spoiler

In truth, she is not a demon. she is a normal Beastman. However, she was the one who picked up Touka's Halo, granting her great power. The monsters started calling her Demon King after that.