Rui Sasaki, age 25, is single and has never been with anybody. People often tell her how young for her age she looks, but even she wants a chance at romance.
Luckily for her, a night out with a childhood friend leads her to meet the calm and very handsome Ritsu. Though most of the night ends in a blur, when Rui wakes up with Ritsu in her bed, she can only draw one conclusion... she's finally done the deed!
Ritsu, meanwhile, confesses that he has a problem... she's the only woman he's ever been able to sleep with!
Will their one-night fling blossom into romance? And can two people, each with their own complicated feelings about love, find a happy ending together?