Due to an incident in their childhood, Taeeun's father owes a debt to Sooyoung's family, sending them one million won every month.

Years later, the two reunite as adults when one is appointed the new team leader and the other is the youngest member of the team, beginning a precarious life at the office.

"Team Leader, why are you so good to me?"

"Because I owe you a debt."

"Then why do you hate me?"

"Because I'm not sure if that's part of the debt I owe."