the truth is that someone brought it up in a conversation some days ago & I couldn't stop thinking about it ever since
why do exes have to erase themselves from each other's life? why do they fear & run away even from memories?
as you said, it'd be nice & really, it should be ok to reminisce about that past. granted it could be painful to remember the happiness you once had and then had to let go of but it's a part of your life and your history and if they were happy times then they should be appreciated rather than dreaded
the funny thing is I'm one of those who think you can't be "pure" friends with an ex (because feelings somehow linger as you beautifully portrayed it here through Junmyeon) but it doesn't mean they have to be enemies or something. they can still be on friendly terms...

lol! look at that. I should stop here before it gets embarrassangly longer