Isaku Senagaki is the beloved granddaughter of a family of gangsters -- and always close by is Keiya Uto, the overprotective first lieutenant that went so far as to fabricate his age to enroll in high school with her to fend off those nasty boys. An innocent young girl and a man of the criminal underworld. Isaku and Keiya are poles apart, but they finally overcome their differences to become sweethearts, madly in love with each other!

Isaku is over the moon, but who should find out about her big secret but the leader of the yakuza clan, her grandfather himself? Meanwhile, Shido, the leader of an affiliated yakuza organization, turns up on their doorsteps. He has a history with their family and her mother, and Isaku will need to come to terms with what this means to her.