I've seen this piece used as an avatar quite a few times, and I've discovered that the people who use it usually aren't aware of it's source. So their reaction when you tell them where it's from is usually pretty interesting!

Grandotron said:

I've seen this piece used as an avatar quite a few times, and I've discovered that the people who use it usually aren't aware of it's source. So their reaction when you tell them where it's from is usually pretty interesting!

According to this e-shuushuu post, the image was created from a game cg.

• http://e-shuushuu.net/image/200017/

EDIT:
I was wrong. The image is directly related to this game CG:

• Mahou Shoujo Ai ExtraStory ~The end/latter part~
• http://www.ascii2d.net/imagesearch/similar/1b2d84b7f80a3d76fc7c98290384b7f8