Fifteen years of loving his childhood friend, and he was the one man she wouldn't sleep with.

Kang Yoon had finally decided to confess to Yoo Haon. Then, at a department party, he found her kissing another man in a dark alley.

Haon had no shortage of men in her life. She had slept with more than twenty, but Yoon was different. She didn't see him that way. She wanted him to remain her best friend, someone who would always be there without ever asking her to change.

Heartbroken and drowning his sorrows in alcohol, Yoon unexpectedly crosses paths with Han Haewoon, a beautiful classmate whose reputation has been ruined by a cruel rumor.

Their relationship begins with an unusual arrangement: they become partners in name, but their relationship soon develops into something neither of them quite expected. After a night together and a few days of living under the same roof, they gradually become the person each can turn to without hesitation.

Meanwhile, Haon begins to realize what it means to lose the one person who has always been there for her.

Yoon spent fifteen years waiting for his childhood friend to choose him. Perhaps it's time he stopped waiting.