Wow, I was actually looking for the full version of this picture for a while, then all of the sudden it appears on the frontpage here. Good thing I listed to the sudden inspiration I had to check this site.
Creayus is a great artist; she only recently made a pixiv account and started uploading things, though. Otherwise you can find stuff at her homepage, but it's usually in low quality.
Edit: Years later, editing this because it falsely represented Rangetsu/Creayus' gender!