The red string quest thing was so they could fall in live again, the chapters of their past life was the rock showing them what happened when they choose to stay together, so now the rock gave them a chance: you can choose to stay together knowing what's the worst that could happen or forget eachother and move on with their lives, Yeon asked Kihoon to forget him so he could have a bright future but Yeon choose to keep the memories, then they just skipped to the future
Hopa this helps
I hope your pillow is always cold at night you angel cuz I was so lost during those chapters
oooh I get it now, thanks a lot <3
Didn't understand hehe