Gayoung's life seems complete after Kyungsoo confessed his love to her. Kyungsoo who is a top student and well-known for his good behavior in their school is her boyfriend. They make their own bubble of happiness as a lover. Gayoung can't ask for more than this, not when she's together with love of her life.

But it's not until a certain someone, named Kim Jongin, came into her life. Perturbing Gayoung's bubble and almost destroying it.

Kim Jongin is everything that Do Kyungsoo not. He is the bad while Kyungsoo is the good.

Back from States after 5 years, Kim Jongin meets someone who's attractive and enough to make him crazy. In his life, the word of 'give up' isn't exist, even after he knows that Gayoung is taken already.