College student-cum-pianist Su-yeon goes into a destructive spiral after he messes up his piano performance. And he's decided getting into bed with strangers is the best way to cope with his anxiety. When he's sleeping with someone, it's like all his troubles just melt away—like he's underwater. During one of his meltdowns, he ends up sleeping with Hae-su, a student-athlete. Except Su-yeon has no memory of the incident. Hae-su remembers it all however, and when the two end up working together on a group project, he is determined to break down Su-yeon's walls. Hesitant at first, Su-yeon gradually discovers that there's more to life than just being surrounded by shades of blue. Will Hae-su be able to pull Su-yeon from the water he's submerged himself in or will the current be too strong to...resist?