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?

It’s almost Yuri’s birthday, and Keiichiro’s present for her is none other than a three-day trip to Kyoto! But as always, the couple isn’t allowed any intimate contact… How will Keiichiro’s birthday surprise for Yuri turn out?