Unfortunately Janes seems to be the only reputable source for this mysterious YJ-12, and any other mentions of it seem to be clones of the janes article.
Personally the lack of photos of such a missile -- even no reputable drawings or CGI -- after all these years make me think it may have been shelved or cancelled a while ago. I personally think a light-medium weight supersonic SSM should be developed, but something like brahmos and granit aren't the way to go. Rather, japan's SSM-3, and the proposed perseus missile are both better examples. Not as massive as the russian missiles, stealthy, and with both active radar and EO guidance.
As to the Russians -- well technically the brahmos fits your requirements, although it can be argued to only be a development of the yakhont. They're certainly ahead in the large supersonic anti ship missile race, but at the moment I don't think china's even competing in it.
the PLA seems to be focusing on a mass of much lighter, subsonic anti ship missiles like YJ-82 and the longer ranged YJ-62. However the AShM industry seems to be diverging into two directions now -- subsonic, stealthy, long range, and supersonic, stealthy, and shorter range. The PLA should invest in both.