is kanariya a B-Side track???? O_o

[Yukitora]

HEAVEN may be a "double a-side" single...

It wasn't. Will was it's b-side, which is why it was called "HEAVEN c/w will"

yep. not all c/w are B-sides. Take GAME for example. The only three b-sides she have are Ever free, Two of us and Theme of A-nation 2003

GAME was a b-side i'm sure. You are also missing alterna which was also a b-side.

B-sides do not mean they are not allowed to have many promotion at all. That is a misconception. It just means that they are not a "main track". The name derives from when singles were released on 12" inch vinyls where one song appeared on the same side (a-side) and as an extra, there was another song on the other side (the b-side).

Or in other words, a song "came with" ("c/w") the single.

Again, you can't have a b-side single if there is only one original track.

Also b-sides can appear on albums. Many don't but that is simply because it was decided that they wouldn't. Lately Ayumi has also put in lots of effort to make her b-sides the same quality as her a-sides, so it would be a waste if it weren't put into her albums.