Yoshimori's older brother who works for the shadow organization.
As the oldest son of the Sumimura Clan, Masamori was trained to become a kekkaishi. Masamori furthered his training s he grew. However, because he did not receive the Houin mark, he was denied access to the scrolls passed down by his ancestors, meant only for the eyes of Legitimate Successors. From that he saw himslef as a outcast and became part of the shadow organization. As a child, Yoshimori drew the Houin mark on Masamori's hand in an attempt to cheer him up. Both brothers have a habit of staring at and flexing their hands. Yoshimori wondering why he has the Houin, and Masamori wondering why he doesn't.