Rin Okumura is a teenager with a natural gift to get himself in trouble. Despite that he tries his best to meet the expectations of his twin brother Yukio and Priest Shiro Fujimoto, who acts as their guardian, until he finally learns about the dark secret behind his origin.

Suguro's joint strategy pays off, and the Exwires have success in their sights! But then a gigantic moth demon (cuchi) appears, and attacks Rin the moment he lets his guard down!

Ernst is scheming to open the Gehenna Gate by using the blood of Rin, son of Satan. In order to protect his wounded older brother, Yukio offers to take his place.