Mono Shinobino is a first-year student at Itan Private High School and a classmate of Shoko Komi and Hitohito Tadano in class 1-1. His appearance is unmistakably ninja-inspired: he wears the standard school uniform along with a black scarf, a bandana, a face mask, and fingerless gloves, and he keeps his black hair tied up. Despite this overtly stealthy look, he is not particularly secretive or quiet; he frequently speaks up during class activities and socializes openly with his close friends.

His name is a homonym for the Japanese phrase shinobi no mono, meaning a person in hiding, which plays on his visual theme rather than his actual behavior. In terms of personality, Mono comes across as an ordinary, sociable teenage boy. He is part of a small group of male friends that includes Chiarai and Sonoda, and the three are often seen together discussing everyday topics, such as which of their female classmates would be the best to date. His role in the story is that of a background supporting character, providing glimpses of typical high school life and peer interactions among Komi’s wider circle.

Mono does not undergo significant personal development or display any special abilities; his presence mainly reinforces the everyday setting and the diversity of classmates at Itan. His key relationships are within his trio of friends, and he has no particularly deep connection to the main cast. Overall, he functions as a lighthearted, recurring background figure whose appearance and name create a contrast between his ninja aesthetic and his open, unguarded manner.