Tanishi is a male high school student supporting character. He has grey hair, black eyes, and a buzz cut hairstyle, typically wearing a standard school uniform with a tie. Tanishi frequently entertains inappropriate thoughts, particularly about his classmate Eriko. During encounters at railway crossings, he fixates on her physical appearance, experiencing perverse impulses. He deliberately waits with her at these crossings to observe her figure from behind. Despite these feelings, he harbors no realistic expectations of a relationship with her, primarily due to rumors suggesting she has a boyfriend. His character lacks documented development, background story, or familial history. His role is similarly undocumented in other narrative formats like movies, OVAs, or spin-offs. His interactions are confined to brief, everyday scenarios centered around railway crossings, consistent with the series' slice-of-life structure.