When the city built down, we ran to the forest and promised to never build again.

I think one of the greatest pains I've felt is watching people you've cared about move on.
I guess you do feel happy for them but there is always this feeling of betrayal.
And as much you don't want to feel that pain, you're the one who has been left behind.
Oh the things I would change, if i could.

How could this happen to me 
But even worse, how could this happen to you 
Meaning behind the song