I GOT IT!
OK, implementing KLin's idea(s) and my repeatitive listening of the song, I've decided to do some of this:
Everytime the singer says "I" It'll be Cain. "My Love" and "you" will of course be Shido. Near the end, when it starts talking about "her" That'll be Riho. The person who died, Shido's Bloody Valentine, will be the Human Riho.
It will still be action orietned. Cain will be lip syncing some parts, such as
"Oh, my love
Please don't cry
I'll wash my bloody hands and
We'll start a new life
I don't know much at all
I don't know wrong from right
All I know is that I love you tonight
Tonight"
Although, since you know I'm in love with transparencies, I might just have Cain 'singin' and then stuff going on in the background. Since Cain really isn't trying to change his lifestyle for Shido, but rather, trying to get Shido to come back to Cain, it will sort of be a Nightwalker alternate reality type thing.
Thanks again, KLin!

