Ritsuka's older brother. He was seventeen when he was found murdered, although he died under mysterious circumstances and could only be identified by his dental records.

When Ritsuka lost his memory, Seimei stepped in and became an extremely important figure in his life. He protected Ritsuka from their abusive mother, Misaki, and was a great source of comfort and trust. As a result, Ritsuka was hit hardest of all by the news of his brother's death. He is very bitter and vengeful towards those who may have been involved in the killing of his brother.