Momiji Fujimiya is the primary protagonist of Blue Seed and a descendant of the legendary Princess Kushinada from Japanese mythology. She was born and raised in Izumo, a region closely tied to the ancient myths, and initially led a relatively ordinary life as a middle school student. Although her grandmother regularly performed purification rituals and reminded her of a greater destiny, Momiji did not fully grasp the significance of her heritage until she was confronted by Mamoru Kusanagi, a cat-eyed man with magatama beads embedded in his hands, who called her Kushinada and attempted to kill her. This event thrust her into a hidden conflict between humanity and the Aragami, supernatural plant-like monsters spawned by the eight-headed serpent Yamata no Orochi. As a Kushinada, Momiji carries the Kushinada pulse in her blood, a powerful force from the Age of Legends that can send all Aragami into an eternal slumber if she is killed. The Aragami therefore seek to contain or sacrifice her, while human forces wish to protect her. During an attack by the powerful Aragami known as Orochi, Momiji intercepted a fatal blow meant for Kusanagi and was impaled. Instead of dying, she was fused with a mitama, a fragment of an Aragami soul, which became embedded in her chest. This event endowed her with the ability to sense the presence of other Aragami, a power that proved invaluable to the Terrestrial Administration Center, the secret agency charged with fighting the monsters. She subsequently joined the TAC under the protection of Kusanagi and the supervision of director Daitetsu Kunikida, initially to learn more about the twin sister she never knew she had and to understand her own destiny. Momiji is characterized by a highly optimistic and proactive outlook on herself and humanity in general. She tends to look on the bright side of even dire situations and possesses a natural initiative, though she becomes very shy and hesitant when it comes to matters of love and romance. Her optimism and resilience are central to her ability to endure the horrors she encounters and to resist the corrupting influence of the mitama within her, which she can keep at bay through strength of will. Her relationship with Mamoru Kusanagi is the most pivotal in her development. He begins as her would-be killer but quickly becomes her dedicated protector, and over time they develop a deep bond. Momiji eventually confesses her love for him during a crisis in a shielded town, and he asks her to wait for him in return. She also forms a close, almost paternal relationship with Mr. Kunikida, who treats her with kindness and refuses to exploit her abilities as he did with her twin sister. The discovery of her identical twin sister, Kaede Kunikida, whom she never knew existed, adds a layer of personal tragedy and complexity to her journey, as Kaede is revealed to be working with the Aragami to resurrect the god Susanoo. Throughout the series, Momiji evolves from an unprepared, ordinary schoolgirl into a courageous young woman who actively accepts her role as the Kushinada and stands firm in the face of her predetermined fate. She learns to wield her Aragami-detection ability effectively and draws strength from her belief in humanity and her connections with those around her, ultimately proving to be a central figure in the battle to prevent the destruction of the world.