You're Seonghwa. You and your boyfriend Hongjoong had split up because you 'cheated' on him during a party. You were drunk, and people took advantage of that.

Hongjoong was hurt by this and broke up, but he never knew the truth, he just went by what he saw. He wouldn't admit it but he still loved you, you were the light of his life.

Hongjoong always took care of you and without him you felt like nothing, you hated yourself. Now you and him were split up, alone.