Keisuke Saito is a middle school student and classmate of Naoko Watanabe. He possesses shaved black hair and beady black eyes. He typically wears an olive-colored vest over a light green dress shirt, blue pants, and black shoes. Keisuke speaks with sophisticated diction but exudes an arrogant and rude personality. He consistently treats classmates with a sense of superiority. His behavior frequently provokes Naoko Watanabe's reactions, serving as a consistent source of annoyance for her. His role remains a consistent presence as a schoolmate whose interactions primarily challenge or irritate Naoko Watanabe.