I stumbled upon this video just now. It's from one of the Beautiful Days concerts in Japan, back when Ava made her Japanese debut and the show aired on Japanese television. The performance features a bunch of people who, I assume anyway, were part of the show in one way or another. Ava shows up around the middle of the video.
http://www.youtube.com/watch?v=ve6ixmzcQsM
I'm not sure if the song is called Remembering or Remembering Me.
I think the guy with the glasses is Zero. He released some singles in Japanese as well (including the show's intro-song, if I'm not mistaken). Though, he was never in the show, as far as I know. Someone else played him in the show.