He is a talented swimmer with a playful personality who attends the same university as Bok-joo. He and Bok-joo had been childhood friend when they were in elementary school. At first, when they meet again at the university, they do not recognize each other, until an incident occurs that refreshes their memories. He is raised by his kind aunt and uncle after his mother leaves him behind and moves to Canada, where she starts a second family. Joon-hyung suffers from a trauma and often during his tournaments, suffers a panic attack and makes a false start leading to his getting disqualified. He enjoys teasing Bok-joo, but gradually falls in love with her.
