A peculiar kind of succubus, unlike any other kind of monster. They were originally incubi who suddenly transformed into monsters. Normally, a human man can never become a monster. As of the present, there are no males among the monsters at all. When it comes down to it, an incubus is just a human warped by mamono mana. Due to the existence of essence, which human men continually produce, no matter how strong the mamono mana that's imbued in their body, human men remain human.