You and Heeseung are married and had a divorce

While walking home you throw your ring on the ground

The next day

You woke up, you look young again, and you notice everything looks old, you check the calendar and you saw it was 1997, you are back on your 4th year high school, the year you met Heeseung

At school

You we're so happy when you thought you can change the past, while you are walking to your classroom you walk past Heeseung