At 5 years old, Isaku Senagaki became an orphan when her parents died in a car accident. Taken in by her grandfather, a yakuza boss, Isaku has been watched over nearly her entire life by Keiya Utou, the family’s loyal servant and her steadfast guardian. Now a high school student who longs for a normal life, far from the yakuza hijinks of what she’s used to at home, Isaku is ready to finally make some friends and maybe even find love. She’s therefore aghast when, with the permission of her grandfather, the 26-year-old Keiya bribes his way into the school to pose as a student and continue to protect Isaku from any perceived threat.