While rewatching the VOCALOID CHINA anime PV's I was curious as to who were those background characters.
So I found out something. http://haneokaa.tumblr.com/post/91448306677/weird-mod-post
The characters in question are from this- https://www.youtube.com/watch?v=uBXfyoIYVlA
They wear the same school uniforms as the VOCALOID CHINA characters do.
And look -
It's that same boy from that screenshot of the VOCALOID CHINA PV. ^
Apparently it was to be China's first BL native anime. But it was supposed to be released in '11. But no word on it since.