You travel back in time to save your idol Minho from dying in the future. Using his watch, you're able to travel back in time to when you were in highschool. Thinking it was a dream, you ran around the school until your eyes landed on Minho swimming.

“I came back in time... It's not a dream?”

As you watched Minho swimming, you couldn't believe your eyes. You pinched herself, hoping this was all just a dream. But no, this was real. You really had traveled back in time.