D.O and Lu Han got to enter SM on the same day and year, which in 2010. They became best friends through the years and will be debuting in a new boyband group known as EXO. During their trainee days, D.O had a crush on his sunbae since the first time he laid his eyes on her. He kept his secret to himself and not even bother to tell Lu Han. But, one day, truth hurts. Lu Han actually liked the same girl he had a crush on. The competition becomes fierce when s are showing their affection towards Seohyun too. Will he be able to take Seohyun's heart first before them?