His rule: No sexual relations until age 18! Her rule: No rules.

Free-spirited Yuri Hasegawa and straitlaced Keiichiro Katsuragi have fallen in love. But his elite political family—producing a line of prime ministers—does not allow male descendants to engage in any sexual relations until they are 18. Can the physically affectionate Yuri and rule-abiding Keiichiro keep their relationship strictly chaste?

Yuri and Keiichiro are up against the final boss—Keiichiro’s grandfather—who gives them an ultimatum: choose the girl or leave the family. Yuri and Keiichiro are driven into a corner, but weren’t they meant to be together?!