Hoshu Washin is a nation ruled by four clans. Kenshiro, the ruler-in-waiting of the Totsuki clan, prefers to spend his time chasing skirts and abhors the training he's forced to endure on a daily basis.

One day, the Totsuki clan is attacked by mysterious beings in Oni Masks. Kenshiro vows revenge and sets off on a journey to bring them to justice with his faithful retainer and friend, Tatsuto.