Yoshiro Kanata was a High School student who had a simple wish, to see his mother once again. His mother dissapeared the day he was going to celebrate his fifth birthday, and her room was sealed, not letting him, nor his sister inside. When Yoshiro breaks in the room the day he was scolded at by the teacher, he notices the mirror hanging next to her bed was glowing, and when he touced it, he was transported to another world called Helengekia. There, he finds a kind girl, Red Tsuskimi who helps him try to find a way back. When they realized he couldn't get back, his life in Japan ends and begins again in Helengekia.
In the epic conclusion to the Devil's Deal series, Freya has one final chance to discover the full potential of her own power, and to use it to restore balance in the universe - once and for all. After the destruction caused by Roisin, Ferya and Torix come to terms with their losses and mistakes... And prepare for a final battle that will change everything.