Joo Seo-ah and Nam Dohyeon have been inseparable friends since middle school, sharing a bond that always felt like equal ground. However, following the implementation of the new age unification law, a technicality shifts their dynamic: Dohyeon is officially younger than Seo-ah. Heartbroken by a recent breakup and nursing a specific craving for the comfort of a firm, youthful younger man to spite her ex, Seo-ah decides to exploit this sudden age gap. She turns to Dohyeon, whose birthday falls just months after hers, and issues a playful yet daring challenge. “Hey, Nam Dohyeon. Call me Noona,” she demands. To her surprise, Dohyeon actually stammers it out, looking flustered and endearingly shy. Seeing him blush makes Seo-ah’s heart skip a beat; she suddenly finds him dangerously cute. Panicked, she realizes she’s crossing a line she can’t uncross. If he starts looking this adorable, she’s in serious trouble. What on earth is she supposed to do now?