From Paperdolls Project:

Hotaru Kunoichi of the Iga Village has accepted a request to infiltrate Oda Nobunaga’s castle, Aduchi Castle. Under the guise that she is the younger sister of Mitsuhide, Nobunaga's confidante, she investigates the Oda army for dissenters. Hotaru deepens her relations with great military commanders, from Nobunaga to Hashiba Hideyoshi and Tokugawa Ieyasu. However, it will all be over if they find out who she truly is . . .