Bantaro Sanbonmatsu is Jiyu Nanohana's classmate at Hontsuru Junior High School. He leads a tightly-knit group of friends, proudly unrefined in nature, originally consisting of Kozaru and Ozaru, later joined by Shirou Ryujoji. From their first meeting, Bantaro harbors an intense romantic interest in Jiyu, driving him to attempt multiple confessions of his feelings. Each attempt, however, is thwarted by persistent misfortune and coincidences. Undeterred by these failures, his constant proximity to Jiyu ultimately leads him and his friends to uncover her secret identity as the successor to Yagyu Jubei. Aware of her double life, Bantaro is motivated to support her against recurring enemies. Despite his dedication, his efforts repeatedly prove ineffective due to his lack of combat prowess and intellectual limitations. This perceived lack of intelligence draws frequent criticism, especially concerning his expected future role of taking over his family's traditional sake brewery business. A distinctive aspect of his appearance is the dynamic kanji characters displayed on his shirt, which shift in real-time to mirror his current emotional state, the conversation topic, or the immediate situational context.