During the end of the shogunate, there was a group of black-clothed masked samurai known as the "Crow Squad" who resisted the shogunate's oppression, taking down key figures one by one. During a Go game with a visitor named Seki Hikonoshin, the government inspector, Nozoe Minbu, was attacked and killed by what appeared to be the Crow Squad. The witness, Yoshi Goro, was also injured by their blade. Minbu's son, Katsuma, returning from a trip, learned of this and, along with his sister Sakura, vowed revenge.