Kôkin Shûryu (also romanized Koukin Shuuyu) is the 16-year-old cousin and childhood friend of Hakufu Sonsaku. Raised together like siblings after Hakufu's father entrusted her to his family during wartime, he attends Nanyo Academy and eventually joins the school's elite Big Four fighters, replacing Kouha Kannei. Despite possessing significant combat potential and strategic acumen comparable to top-tier fighters, his shyness, lack of confidence, and limited battle experience keep him ranked C-tier. He appears frail, with dark blue hair covering his forehead and reaching the back of his neck, and typically wears the Nanyo Academy uniform: a light brown vest, button-up shirt, and black pants. Shûryu is deeply loyal to Hakufu, vowing to protect her at all costs, even at the expense of his own life, and harbors longstanding romantic feelings for her. His development centers on protecting Hakufu and honing his abilities. In early manga events, he intervenes in her fights, trains with her, explains the magatama ranking system, and battles Nanyo fighters to reach her, resulting in hospitalization after losing to Genpou Saji. He tirelessly searches for Hakufu during her periods of distress and supports her recovery. In the anime, rivals kidnap him; he escapes to negotiate Hakufu's safety through combat and participates in tournaments, though injuries often sideline him. He later helps Hakufu temporarily control her dragon's power and prevents her from killing an ally. During *Dragon Destiny*, he initially seeks revenge against Seito for harming Hakufu but abandons this path upon realizing it contradicts her wishes. He joins the Battle of Red Cliffs, defeating the stronger Chuukou Kyocho by using chi-infused wires to trigger debris. His relationships include unrequited love for Hakufu, with mutual kissing occurring occasionally. He attracts romantic attention from others, including Kan-u Unchou in non-canonical English adaptations. A widespread misconception about him being raped is clarified as false; he only fainted during an encounter with Shigen Houtou. In *Great Guardians*, he appears with no new character development detailed in available sources; his role remains consistent as Hakufu's supporter within Nanyo Academy's conflicts.