The Vocaloid character Kagamine Len. Fan arts of characters don't necessarily stick to the same designs as the original, so you may have someone draw him like this (with his twin sister Rin) and then have someone else draw him like this.

Vocaloid is a voice synthesizing music program. You can probably find several 'songs' created by people being sung by the Vocaloid characters, which include (most popularly) Hatsune Miku, Kagamine Len and Rin, Megurine Luka, or older versions MEIKO and KAITO. It's quite a phenomenon in Japan, and fans have created their own versions of Vocaloid characters. But so far, only those are the official ones.

Here's one of the more popular songs that feature Len's voice: Fire Flower.

Really though, that avatar design is juuust generic and small enough to be anyone. I think it's most likely to be the Vocaloid dude though.