ONA
Description
Kōhai-chan is a 24-year-old office lady working in the sales division of a trading company. She stands 161 centimeters tall and has brown hair, often styled in a ponytail or half-bun, brown or deep-blue eyes, and a distinctive small mole near the corner of her right eye. She originally comes from Sapporo, where her younger brother still lives, and moved to Tokyo to attend university.

She is bright, honest, and naturally cheerful, which makes her well-liked among her coworkers. In the office she is regarded as a capable and promising new employee who learns quickly and handles her duties with diligence. Despite her composed professional demeanor, she has a tendency to act in an absentminded or unintentionally provocative manner around the person she trusts most. She is also aware of her own appeal and sometimes uses it playfully, though never with ill intent.

Her primary motivation is to grow into a reliable member of her team while deepening her bond with her senior colleague, who serves as her mentor. She clearly holds strong romantic feelings for him, but she approaches the relationship gradually through small gestures, shared work, and personal time outside the office. She actively seeks out opportunities to be near him, such as joining him for drinks after work or visiting his apartment under the pretext of seeing his cat. However, because she behaves more formally and cautiously around others, he does not realize that her actions toward him are special.

Kōhai-chan serves as one of the main heroines in the series, representing the office worker side of the story. Her episodes center on the subtle, everyday interactions between her and her senior, as well as her navigation of workplace dynamics and social expectations. In her role, she provides a contrast to the student heroines and embodies the theme of finding warmth and motivation in otherwise mundane Monday routines.

Her key relationship is with her senior, whose name is never given. Their connection begins as a standard mentorship but gradually deepens into a close partnership, with colleagues frequently assuming they are already a couple. She also has a long-standing friendship with Rikei-chan, a university acquaintance who often recruits her to cosplay at Comiket. Another notable detail is that she lives in the same apartment complex as Maegami-chan and Gimai-chan, two other characters in the series.

Over the course of the story, Kōhai-chan becomes more open and relaxed around her senior. She spends increasing amounts of time at his apartment, shows vulnerability when drinking, and learns to balance her guarded public persona with the trust she places in him. Her earnestness and gradual emotional availability drive the development of their relationship.

Among her notable traits is a severe lack of tolerance for alcohol: when she drinks, she quickly becomes intoxicated and loses control, a tendency she inherited from her mother and was warned about by her father. In her professional life, she is skilled at office work and has a knack for deflecting unwanted romantic attention by fabricating a story about a long-distance boyfriend. Her physical appearance, particularly her well-endowed figure, is frequently noted by other characters and is a recurring element in her scenes.