The era is the Warring States Period.

Hotaru is a ninja from Iga who is sent to infiltrate Azuchi Castle, stronghold of the warlord Oda Nobunaga and Akechi Mitsuhide Nobunaga's confidant.

"I've decided to keep you..." She ends up working for Oda Nobunaga and impersonates Mitsuhide's sister in order to stay in the castle.

Azuchi Castle, Nobunaga's home... What is with these feelings that begin to grow between Hotaru, the warlords and Nobunaga?