Seohyun is an innocent 17 year old girl. Her grades are perfect, she's healthy and fit, and is a star at tennis. But what happens when her summer gets twisted around and she ends up befriending the school's heart throb an bad-boy: Yonghwa? At first it start out as an unlikely friendship, but soon romance finds itself intertwined in their path as they accompany each other in the adventures that summer brings.