In an era of violent social upheaval, a young girl named Tominaga Sei, hoping to avenge her wrongfully murdered father and brother, disguises herself as a man, takes the name Kamiya Seizaburo, and joins the Mibu-Roshi--soon to be known as the Shinsengumi--an elite corps of swordsman who risk their lives to defend Japan's shogunate system. Will she be able to become a warrior and keep her secret intact?