Castle Morihisa is a roguelike strategic deck-builder. You need to build up your deck through constant battles, acquire powerful talents, and wield the power of the Fallen Heroes to unveil the truth behind the rebellion in Castle Morihisa. When facing difficulties, you could also ask for assistance from the Sengoku fallen heroes with different skills, which could give you an edge during the battles.

After general Tokugawa of the shogunate issued the "Laws for the Military Houses" to his vassals, none of the emissaries sent to the Ishikawas in Castle Morihisa have returned. Rumors claim that Lord Ishikawa Shinjuku was attempting to usurp the throne, and that he closed off all roads to the castle a few days prior. The great metsuke Yagyū Munenori requires a spy to make their way to Castle Morihisa to learn the truth of what is going on.