Gifted basketball player, Koh You, and brainy student, Go Jun-hee, are famous for their bromance in high school. Both of them were raised by Jun-hee's grandmother and have completely opposite personalities, habits, tastes, and ideal types. They have never had a chance to conflict, but one day a beautiful transfer student named Han So-yeon shows up.

At one moment, both Koh You and Jun-hee fall in love with So-yeon. Even though she maintains an indifferent attitude, Koh You can't help but care about So-yeon. Meanwhile, Jun-hee becomes increasingly anxious about his poor health condition and repetitive tinnitus.

Jun-hee is rushed to the emergency room in critical condition. He is diagnosed with chronic renal failure, the same disease that his deceased brother had. Koh You is overwhelmed with grief and makes a life-time decision.

Koh You and Jun-hee return to school in better condition. They are once again captivated by So-yeon and her smile. The upcoming party brings anticipation, and it remains uncertain who will accompany So-yeon to the event.

Koh You and Jun-hee sense subtle tension between each other due to their feelings for So-yeon. Jun-hee is confused by the transformations occuring within his mind and body. While Koh You attempts to get closer to So-yeon, he witnesses something unbelievable.

After discovering So-yeon's secret, Koh You is in shock and contemplates whether to give up his feelings for her. Meanwhile, Jun-hee continues to worry about So-yeon, who is left alone, and secretly follows her as she cries.

Koh You senses Jun-hee's changes and hopes it's because of cellular memory syndrome. The conflict between Koh You and Jun-hee intensifies after Koh You discovers So-yeon's secret. What will happen to their longstadning, stable friendship?

Facing an unexpected farewell, Koh You and Jun-hee express their true feelings to each other. Even though he tries to return to a normal life, Jun-hee feels more difficulties in sharing his pain with Koh You.