Hotaru, a kunoichi from Iga Village, accepted a mission to infiltrate Oda Nobunaga's Aduchi Castle. Waiting for her there was Nobunaga's confidant, Akechi Mitsuhide. Under the pretense of being Mitsuhide's younger sister, she resides in the castle and resolves to investigate the internal state of the Oda army to determine if anyone poses a threat to Nobunaga. Hotaru strengthens her bonds with prominent military commanders, including Nobunaga, Hashiba Hideyoshi, and Tokugawa Ieyasu. However, everything will come to an end if they discover her true identity...