Ha-yeon, an ordinary second-year high school student, heads to Upo-ri with her parents for summer vacation. Struggling with friendships and family relationships, she unexpectedly meets Yu-gyeom, the young heir of a traditional Korean family. The two then experience something unbelievably mysterious.

Ha-yeon goes to Upo High School for extra classes. After sharing a special moment with Yu-gyeom, she gets angry at him for already having a girlfriend. However, Yu-gyeom continues to ask Ha-yeon to keep seeing him. The two share another special moment. When Yu-gyeom’s girlfriend, Sae-ryeong, finds out, she visits Ha-yeon late at night.