Midori Kisaragi stands as Toshio Ōtomo's closest friend and classmate. He nurses a shy romantic attachment to Yū Morisawa, relying on Toshio's intervention to convey his feelings. His role frequently leans into comedy, casting him as an accident-prone companion to Toshio who endures physical mishaps. Physically overweight, he displays an avid appetite, with food ranking among his foremost passions alongside his devotion to Yū.

He demonstrates fierce protectiveness toward Yū, clashing sharply when others—including Toshio—mock or demean her, particularly when Yū's emotions are trivialized. Academically, he struggles with poor grades, a fact Toshio openly observes. Interactions paint him as a gentle giant: physically imposing yet typically timid. However, his unwavering romantic pursuit of Yū—a younger elementary school student while he attends middle school—introduces tension. His documented traits remain consistent without expansion into other narratives.