[Succubus]

Koa is on the verge of failing the summoning magic class and having to repeat his year again, he stumbles upon an ancient Grimoire and uses it to summon a sealed succubus Katie making her his familiar. She has been feared "devil" since ancient times and possesses tremendous power. As a familiar, necessitates magical energy on a daily basis. Kairi, Koa's childhood friend, grows unsure of their relationship while other students are also taken back by his familiar.