At first I thought Ukon, but no holy shit that's an old model I haven't seen for years. I believe its apart of a DeviantArt kit bash of MMD assets. The hair is super popular among TDA models, but it I believe was on the first edition of the second model of Ukon. I could be wrong, but you can easily get that hair at least, as for the avatar I'm unsure. If you remember the name or author of it in game I might be able to assist. Otherwise DeviantArt has a bunch of DLs when you look up MMD models, but you'd have to go through the conversion process.
