Son Wendy makes a vow: to never fall in love again after her last relationship. Soon after the departure of the captain of the elite team, REVE Legend, Wendy was force to join the team. She soon found herself in the middle of troublesome situation and an unexpected reunion between her and the team's captain, Bae Irene. Can she keep the vow that she made or fall in love for their captain?

Son Seungwan also known as WENDY is a notorious, cold-blooded, heartless girl that assassinates people as her profession. She’s one of the heiresses of the strongest clan in the assassination world that hides under the shadow of the moon. One day, she received a mail coming from her father about an mission that later will change her surroundings and to herself and the one that will break her vows.