Baek Minseo always had a huge crush on her senior, Kim Sunggyu. But Sunggyu only thought of Minseo as a little sister, while Sunggyu had a crush on another student in Minseo's class, Oh Hayoung. Then there is Jang Dongwoo, who was always there for Minseo, someone for Minseo to lean on. How will this complicated love story turn out?