Your fanart is beautifully rendered and has amazing detail and emotional impact!
However, I gotta say... I don't think the characters look true to their ethnic backgrounds. Chihiro here, to me, looks Chinese or Korean, where she is certainly Japanese... and I noticed San, in your other painting, looked east Asian.
I wonder if this is intentional, or if perhaps it is because of your references.
I do like the chinese-style dragon prints on San's clothes, so I can see why you might make her look Chinese.
I also love the colors you chose for this piece. The dramatic lights and darks really fit the mood.
Is there a legitimate 'ethnic' look separating Korean from Japanese, outside of clothes and posture?
Definitely the shape of their faces, but mostly the eyes, comes into play when speaking about these three nations.
It's a little hard to describe -for me anyway- but when you look long enough you get to notice the (actually quite obvious) differences between Japanese, Korean and definitely the Chinese. And in this painting Chihiro looks closer to Zhang Ziyi then she does to say ... Hikaru Utada.