The Matsuda family, known for their fighting techniques, must defend their empire against an impending invasion. Misaki, a mother and wife, must confront her violent past to protect her family. Meanwhile, Mamoru, a young member of the Matsuda family, realizes that the empire he was bred to defend may be built on lies. Set in a world of superhumans and powerful warriors, 'The Sword of Kaigen' is a tale of family, loyalty, and the struggle for power.