Sakurai Yuki was abandoned by his mother and left in an orphanage, where he spent his childhood alone. Now, as a high school student, Yuki has recently begun to have several mysterious dreams that leave him with a nostalgic feeling that he has seen it all before. In the evening he receives a letter from an unknown sender that leaves him worried by its contents. When he answers the cries for help of a fellow student, Yuki is almost hit by a truck but is saved by the quick actions taken by a mysterious silver-eyed man.

Yuki meets a man who introduces himself as Takashiro Giou, who claims to be his older brother and asks him to come with him to Tokyo. Yuki is initially confused by the sudden revelation and as a result (of the female Yuki accusing him of running away) causes his power to break the orphanages' windows. Later, he has a confrontation with Uzuki at school, and his powers almost goes berserk again. Frightened and confused at his growing powers, he runs away only to meet up with Zess who comforts him. As they begin walking, they are attacked by Duras or demons and are saved by Touko and Tsukumo, along with Takashiro who talks about the Giou Clan and how everyone of its members have special powers and that they need his power.

Yuki is troubled after his meeting with Murasame Toko and Tsukumo and Giou Takashiro, head of a family with special powers known as the Giou Clan. Does Yuki belong with Takashiro or with the children of the orphanage? Zess kindly watches over the confused Yuki while agents of evil approach. Zess warns Yuki to remain at the orphanage on Walpurgis Night but that night two orphans go missing and Yuki is asked to help look for them.

While searching for the missing orphans, Yuki receives a call from his classmate Uzuki and heads to school, where he finds someone unexpected. Worried for Yuki, Tsukumo uses his power to find him and heads to his rescue.

Having found his place among the Giou Clan, Yuki decides to travel to Tokyo with Luka and the Zweilt Guardians. On the way there, inexplicable feelings well up inside Yuki as Luka sleeps by his side. Meanwhile, the police bring a case thought to be the work of demons to Takashiro in Tokyo, and two new Zweilt Guardians await Yuki at the police station.