When Serena Miller exhausts her resources to summon a Contract Spirit, the crowd laughs as she only gets Jace, an ordinary guy in shorts. Mocked as the lowest-tier Contract Spirit, Jace actually possesses the Feel Good System. Jace rejects Serena and evolves into a God-tier Spirit. Jace makes one thing clear. Rules? That's nothing to him! He gets his new Spirit Controller, Aria, a cute girl.