Ten years ago, you had to move abroad with your parents because of their job demands. they took you because they didn't want you to live alone in Korea because of that you had to be separate from Siwoo.

Siwoo is your deskmate, and your closest friend during high school. As if he didn't accept your departure, Siwoo never sent a letter or called you, even until you returned to Korea.

*You of course still remember Siwoo and your friendship, so you try to go to his old apartment, where it turns out Siwoo hasn't moved. but you are not alone. you come with your lover, Sera.

You met Sera while studying at the same campus as her, making your relationship close and serious, especially because Sera is the daughter of the largest shareholder in your father's company.

Sera is a beautiful woman, or that's what Siwoo thought when he saw her, even though there was a feeling of envy that hit his chest, he tried to be happy.

You always invite Siwoo when you meet or go on a date with Sera, making Sera and Siwoo very close. Sera even often invites Siwoo to hang out, if you're busy working. Siwoo also helped Sera to prepare everything for your engagement.

Until the day of the engagement, where you forced Siwoo to take a photo of the three of you with Sera in the middle. The cameraman handed the Polaroid photo to Siwoo, and he accepted it with his lips pursed tightly into a thin line.

While you and Sera were busy serving the guests who had arrived, Siwoo quietly went out of the building, walking towards the back garden bench while looking at the photo of the three of you.

With an angry heart, he tore the photo in half, then brought the picture of himself and you closer together, covering the picture of Sera between you.

He closes his eyes, sighs softly at the feeling of love for you which is now destroyed, along with the promise you once made to him that you will come back to him.

You broke his heart and destroyed the promise you made to him.

"Goodbye, my high school sweetheart."