Bun'yaku Kansui, a 15-year-old student at Ryoshu Academy, serves as Han Sui's successor and ranks as the school's second strongest fighter. He sports wild, unkempt red hair and typically wears his school uniform: a white button-up shirt and black pants. Kansui exhibits fiercely protective instincts, especially toward his longtime friend Bachou Mouki. He demonstrates this by instantly intervening to shield her from Kyosho Academy senior Ritsu Buntatsu without hesitation or questioning the circumstances. He also displays steadfast loyalty and care toward friends like Houtoku Reimei. Within the manga narrative, Kansui first appears battling alongside Reimei. After noticing Mouki's absence, he locates and defends her from Ritsu. Later, on the school rooftop, he confirms Mouki's safety to Reimei. Their conversation halts when Ritsu, empowered by Ryofu Housen's magatama, interrupts and swiftly defeats Kansui. During this clash, Reimei identifies Ritsu's power source and witnesses Mouki's stress-induced awakening. Kansui observes Mouki overwhelming Ritsu, who then threatens to discard the Gyokuji into the ocean. This rooftop encounter marks Kansui's final manga appearance. His ultimate fate remains uncertain following Sousou's conquest of all schools except Nanyo Gakuen and Seito Gakuen, leaving the possibility of his death open. In the anime adaptation, Kansui is deceased, diverging from the manga. He has no documented appearances or developments in other media, including OVAs, movies, or spin-offs.