Kazuto Mano is the male protagonist of the series. He is a young man who moved to Tokyo with the ambition of becoming a professional photographer, a dream that ultimately did not come true. Following this setback, he works the night shift at a convenience store to support himself. His living situation changes dramatically when his childhood friend, Yayoi Muto, asks to stay in his apartment, leading to an unexpected period of cohabitation.

In terms of personality, Kazuto is presented as someone who struggles with feelings of being overshadowed by Yayoi's success, as she has realized her own dream of becoming a popular model while he has not. Despite the awkward and tense atmosphere that initially accompanies their new living arrangement, he is accommodating enough to allow Yayoi to stay with him. A key aspect of his personality is revealed through his observations of Yayoi's secretive behavior; he notices she frequently leaves the apartment at night to meet other men, which he assumes are her boyfriends. This leads him to become suspicious of her actions when she is home alone.

Kazuto's primary role in the story is as the point-of-view character whose ordinary life is disrupted by his new domestic situation. His motivations are largely driven by his complex relationship with Yayoi. Initially, he is simply trying to adjust to sharing his space, but the discovery of her secret behavior—turning his room into what he suspects is a personal space for romantic or physical encounters—pushes the plot forward. He is placed in a position where he must confront her actions and the shifting nature of their relationship, which eventually moves beyond simple childhood friendship.

His most significant relationship is with Yayoi Muto, his childhood friend. Their dynamic is central to the story, evolving from a strained cohabitation born of convenience to a more complex and intimate connection. Another key relationship is implied to be with Yayoi's older sister, Kaoru Muto, who is described as free-spirited and may serve as another presence in their lives.

Throughout the narrative, Kazuto undergoes a clear development as he navigates the changing boundaries of his relationship with Yayoi. He begins as a failed artist working a night job, feeling inadequate compared to his successful friend. As he becomes aware of Yayoi's secret and the sexual frustration she experiences, his role shifts from passive roommate to an active participant in a new, more passionate phase of their relationship. The story charts his transition from feeling like an outsider in his own life to becoming directly involved in an intense, romantic dynamic with Yayoi.

Regarding notable abilities, there is no information about any supernatural or exceptional physical skills. Kazuto's primary asset is his background as an aspiring photographer, indicating he has a developed eye for composition and lighting, even if he did not achieve professional success in that field.