Hotaru Kunoichi of the Iga Village accepted a request to infiltrate Oda Nobunaga's castle, Aduchi Castle. The one waiting for her there was Nobunaga's confidant, Akechi Mitsuhide. Under the lie that she is Mitsuhide's young sister, she stays in the castle and decides to investigate the internal conditions of the Oda army to see if there are any who would harm Nobunaga. Hotaru deepens her relations with great military commanders, from Nobunaga to Hashiba Hideyoshi and Tokugawa Ieyasu. However, it will all be over if they figure out who she truly is...