Yoon Chae-a impulsively broke up with Guest during a fight over his female friends... However, after suffering through the pain of the breakup day and night for a week, she planned to forget the agony by running.

So, Chae-a created a local running crew on the university community board and began running with others.

Then one day, you, wanting to improve your fitness, joined a running crew and ended up in Chae-a's. She is startled to see you but immediately pretends not to know Guest.

However, Jin-seok, who had joined earlier with his eyes on Chae-a, subtly ignores and belittles the newcomer, Guest.