Katsumi Amako, a 16-year-old male heir of the Amako Bushi clan, possesses distinctive green hair and red eyes. His clan lost their ancestral home on Awaji Island to oni forces, forging his driving ambition to reclaim it. As heir, he shoulders the responsibility of leading his retainers. Katsumi's personality blends pragmatism and idealism; he initially accepts the Uesugi Alliance's hierarchy but later challenges authority when necessary. He demonstrates fierce loyalty to his men and forges alliances based on mutual respect, notably with Musashi after recognizing shared values.

During the Awaji Island Recapture Operation, Katsumi competes for squad leadership against Akihiro Shimazu and Musashi. When Akihiro assumes command, Katsumi follows orders despite disagreeing with his glory-seeking tactics. His commitment shines through when he defends against oni despite being sidelined, earning reluctant praise from Akihiro. Katsumi confides his history of humiliation and his dream of retaking Awaji to Musashi, strengthening their bond. He later disobeys orders to remain passive, leading his men to independently defeat an oni.

Katsumi participates in the linked attack that defeats Yataro's white serpent manifestation during the battle against the Kishin Orochi. However, Yataro overpowers and cuts down Katsumi alongside other Bushi. He survives only due to Tatsuomi Uesugi's intervention. After recovering, he acknowledges Musashi's crucial role in Awaji's liberation. Katsumi is subsequently taken by Shiro Inukai of the Obsidian Eight.

His abilities include wielding a Kitetsuki sword and possessing a Blue Color of the Soul. His name, Katsumi, meaning "victory snake," reflects his persistent struggle against adversity.