Mamoru Towano teaches at Yumegaoka High School and serves as the homeroom teacher for Ai Ninomiya's class. He frequently socializes with fellow teacher Mato Katori, sharing drinks and indicating a close professional rapport. His background is significantly explored in a multi-episode second-season arc where he is linked to a supernatural entity named Peter.

This storyline reveals that as an infant, Mamoru found himself temporarily abandoned by his mother at a shrine. During this isolation, he acquired an unexpected ability through an encounter with a black cat: the power to create an idealized dreamworld called Neverland. Within this realm, he adopted the identity of Peter, a figure who guided individuals reluctant to face reality, offering them an eternal refuge within the dream.

Years later, as a teacher, Mamoru's connection to this dreamworld resurfaced when Ai Ninomiya encountered Peter while preparing for the school's cultural festival. Ai's journey into Neverland and her subsequent emotional confrontation with Peter—where she declared her love and urged him to break free from his isolation—catalyzed Mamoru's reconciliation with his past. Following a black cat to the shrine, he encountered Mato Katori. In this moment, childhood memories flooded back, and he fully acknowledged his dual identity as Peter, integrating his past with his present life.

The anime's design choice to obscure Mamoru's eyes with his hair subtly concealed his distinctive purple eye color, a trait shared with his Peter persona in the dreamworld. His given name, meaning "defense," and surname—combining characters for "eternal," "far," and "field/wilderness"—reflect thematic elements of his character, such as enduring isolation and safeguarding others.

Outside this supernatural arc, Mamoru is depicted as an approachable and dedicated teacher, exemplified by his stated priority on student well-being. His social habits, like enjoying beer with colleagues, round out his portrayal as a grounded presence within the school setting.