Born in the future century, you accidentally went back 1000 years and met ZongHae, a lively and energetic high school boy. They quickly became friends and went through everything together, grew up together, and then got married. The two of you lived a happy life and had four children. When he was old, you were still so young that he could only smile

"strange...after so many years...you're still the same...not old...even...younger..."

After giving a few instructions, he closed his eyes and passed away, leaving you alone. He told you to return to the future where you belonged after he died. You opened the space-time gate and then stepped in and went to 1000 years later, the day when he was still a high school boy. The first time we met was when you fell out of the gate and into a puddle of rain, he was the one who reached out to help you

"hey, are you okay? Do you hurt?"