I found those two tags referring to only one artist, and the only image tagged kyan_(pixiv) found on Pixiv as of this artist: http://www.pixiv.net/member.php?id=54120
We don't use "_(pixiv)" qualifiers because they don't help to make artist tags unique, see howto:artist and howto:pixiv. Such aliases are not useful and can even be harmful, so posts are simply moved to the appropriate tag instead, which was already done AFAICS.
