TV-Series
Description
Masamori Sumimura is the firstborn son of Sumiko Sumimura and Shuji Sumimura, and the eldest brother of Yoshimori Sumimura and Toshimori Sumimura. Despite being the oldest child and possessing exceptional talent as a Kekkaishi, he was never chosen as the legitimate successor of the Sumimura clan. The mark of the successor appeared on his younger brother Yoshimori instead, a fact that deeply shaped Masamori's path. Dissatisfied with the restrictions and limitations placed on him as a non-successor, he eventually left his family home to forge his own way.

Masamori is a quiet, composed, and highly capable individual. He carries himself with a mature and serious demeanor, often appearing older than his twenty-one years. Beneath his calm exterior lies a complex sense of ambition and a lingering sense of loss. He is frequently seen looking at the palm of his right hand, the place where the successor mark would normally appear, a gesture that hints at his own private feelings of jealousy and longing for the recognition he was denied. His motivations are driven by a desire to prove his worth and to operate without the constraints of clan tradition. He seeks to achieve greatness on his own terms rather than being defined by the role he was not given.

Within the story, Masamori holds significant authority and influence. He joined the Shadow Organization, the overarching body that governs all ability users and ayakashi fighters, and founded the Night Troop, a unit composed of young, promising ability users in training. He rose to become the leader of the Night Troop and secured the seventh seat on the Council of Twelve, the executive committee of the Shadow Organization. His role is that of a powerful ally and a figure of authority who occasionally returns to his family home, though he maintains a degree of distance from his former life.

His relationships are marked by unspoken tensions. With his younger brother Yoshimori, the dynamic is particularly strained. Yoshimori is openly envious of Masamori's mastery of advanced techniques and the way Tokine Yukimura acts around him. At the same time, Masamori quietly envies Yoshimori for being chosen as the successor, though he may not fully acknowledge this to himself. Yoshimori himself often wonders why his older brother, who is so clearly skilled, was not selected. Within the Shadow Organization, Masamori has a notably uneasy and hostile relationship with Ougi Ichirou, the eighth seat, who despises him. Despite these difficulties, Masamori remains a dedicated leader to his subordinates in the Night Troop, guiding many young members such as Atora Hanashima, Kyoichi Hiba, and others.

In terms of development, Masamori's arc revolves around his struggle with identity and legacy. He left home because he could not accept being relegated to a secondary role, and his rise within the Shadow Organization represents his attempt to carve out a place of significance. His journey involves coming to terms with the choice that was made and reconciling his own ambitions with his lingering attachments to his family.

As a Kekkaishi, Masamori possesses overwhelming ability. He is highly skilled in the Hazuma style of kekkai jutsu, the barrier-based techniques used to combat ayakashi. He can execute techniques that are considered difficult for others to master, and his proficiency places him among the strongest human practitioners in the series. His founding and leadership of the Night Troop also demonstrates his strategic mind and his capacity to mentor and organize other ability users.