Ill-prepared for their journey, Musashi and Kojirô found refuge at Samidare Castle thanks to Tsugumi, a mischievous young bushi who led them there. But, as a gigantic wave of oni prepares to strike the place, the lord of the place, Hideo Kosameda, refuses to retreat, even if it means sacrificing the civilians! The only one able to change the situation is Tsugumi, his adopted daughter. However, after years of servility, it is impossible for her to stand up to him! However, Musashi and Kojirô are convinced that she is capable of it and will do everything to allow her to spread her wings.