Living in Roppongi with her lecherous father and grandfather, Teshigawara Saki may come across as a typical high school student. However, she possesses an exceptional talent of unlocking any type of lock. Saki willingly utilizes her skill for anyone who requests her assistance, be it the authorities or members of the yakuza. Unfortunately, as the organized crime situation in Roppongi deteriorates, her willingness to help may drag her deeper into the situation than she would prefer.