A spunky female weightlifter and free-spirited male swimmer meet on campus, only to find out their pasts may be intertwined.
One day Bok-joo, the star of the weightlifting club at her sports university, runs into Joon-hyung, a swimmer who is weak under pressure.
After Joon-hyung saves Bok-joo when she falls into the pool, they realize they were friends in childhood. Joon-hyung comments on Bok-joo's weight.
Bok-joo visits Jae-yi's weight loss clinic but worries about the price. She then hears about a mountain climbing contest with a big prize.
Bok-joo pays the clinic fees and gets an examination, but is warned not to overdo it. Bok-joo wants to thank Jae-yi for lending her his umbrella.
Joon-hyung runs into Bok-joo when he visits Jae-yi at the clinic. Bok-joo hides the truth from Jae-yi and explains that they are just old classmates.
Bok-joo is delighted to get a ride from Jae-yi after the concert. While Joon-hyung is in counseling he recalls an incident from his childhood.
Bok-joo's coach and manager find out she is going to a weight loss clinic and tell her father, who is furious. Bok-joo tries to apologize.
Shi-ho snatches Bok-joo's phone away while she is speaking with Joon-hyung. Bok-joo sleeps in a different room after finding out about the diary.
Jae-yi sees Bok-joo while he is at the university. Joon-hyung tries to cover for her, but Bok-joo confesses to Jae-yi that she is a weightlifter.
Joon-hyung criticizes Jae-yi after he shows up at a weightlifting competition to cheer Bok-joo on, not knowing she doesn't want to be seen like that.
After Bok-joo's disappearance in the aftermath of Coach Choi's firing, she shows up and tells her father she wants to quit weightlifting.
Bok-joo is taken aback at the sight of Shi-ho stuffing her face but keeps it from Joon-hyung. Joon-hyung invites Bok-joo to an amusement park.
Joon-hyung and Bok-joo are now a couple after letting each other know how they feel. Joon-hyung doesn't notice a call from Shi-ho.
Love is in the air as another secret relationship comes out into the open. Bok-joo is nervous after Nan-hee's stern warning to her friends.
Joon-hyung is reunited with his mother. The next day he goes back home to retrieve some childhood photos and overhears something that shocks him.
Joon-hyung goes to the hospital to see Chang-gul, who asks him to hide the operation from Bok-joo so she can focus on her training.