Who's singing WHAT in Kalafina songs??

Atlas Star

Dripping with Kajiura
Feel like I made a thread like this before but I can't find it :p

OK so there are several moments where I just go "who's singing that??" in Kala songs so I thought this could be an open forum for us to discuss and debate.

The one moment I'm hung up on right now is:

KOTONOHA (from 3rd Album "After Eden")
-at the chorus/bridge/whatever you wanna call that part "hontou wa... mou sukoshi... yawarakai... kimichi datta", while HIKARU is on main vocals, who is the upper harmony? I thought it was WAKANA for the longest time even though I had doubts, but now the doubts are returning! It sounds so good and lovely it almost doesn't sound like WAKANA to me anymore.

What do you think? Is it Wakana??