I'm sure someone could source this with the signature timestamp in the upper left corner. I've seen it before, but I can't remember the artists' name.

momocan, aka kei_jiei. Added.

Heh I was going through a few pages of momocan, being all surprised that this wasn't already uploaded before, but it is actually the first (tagged) image of momocan on the server. :D

This one has more contrast, though. Thanks.