Haruka Koyamauchi, an ordinary junior high school student, is taken away and attacked by drug addicts on her way home from school. A mysterious beautiful girl, Mio Kurusu, suddenly appears at the scene and saves Haruka. The next day, Mio appears before Haruka as a transfer student. She is a girl commando on a secret mission from the police. Haruka volunteers to be the commando's assistant in order to help Mio in return for her help. Haruka tells him that it was just a coincidence that she saved him. Mio tells her that his purpose is to help the drug cartel.