Height 170 cm Shidou Itsuka is a student of Raizen High School. He was adopted into the Itsuka family when he was "abandoned" by his mother.

Spoiler

Shidou has the ability to seal a spirit's power. However, the reason why he possesses it is shrouded in mystery. Due to this power which was already known by Kotori Itsuka he was recruited--or rather forced--to join "Ratatoskr" to help and save Spirits. Instead of killing Spirits to prevent spacequake from happening, he has to seal the Spirit's powers with a kiss in order for them to co-exist with humans. Shidou met his real sister at volume 3 which was Mana Takamiya. Shidou, Mana and Kotori can't remember much about what happened 5 years ago because a certain "Spirit/person" locked their memories away, and at that time Shidou met Origami and helped her which was the cause as of why Origami fell for Shidou. Once the power of a Spirit is sealed within Shidou, he has the ability to use some portion of it, thus his resurrection power is from Kotori's abilities when he sealed Kotori's Spirit 5 years ago.