Call me crazy, but I really don't see the similarity to Sasuke people keep mentioning. ~tries to view it from a few other angles~
No, I still don't see it. I mean, the hair is different, with the bangs and the ponytail, and the eyes are nothing like Sasuke's that I can see. The shape of his face, the lips, the nose... I'm sorry, but I just don't see it. Sasuke doesn't have that thin ponytail in the back. For the hairstyle, the only real, semi-similarity are the long bangs that flow down to both characters' chins, and even then, Mathias's bangs only hang that far on one side.
His eyes are a different color than Sasuke's, too, aren't they? Sasuke's are much darker, black or sometimes red, not that lovely shade of light blue. If I remember correctly, anyway, and if all the screenshots and videos I looked up are accurate.
I just wanted to voice my take on the comparison since I really admire Shuangwen's work. All of the original characters, or 'OC's', that she has done have their own special look, including this one, Mathias. The only thing I see him having truly in common with Sasuke is the color of their hair, but that is just my humble opinion. ^.^
The portrait is delightful, by the way! He has an edgy, perhaps somewhat rebellious, look about him that I like.