Normally I despise brooding and emo kid type character, but I think you did a supreme job portraying the character. Consider all the things happened and feeling helpless to deal with the situation he was in, Oki ought to be angry and depressed. Not to mention Shiranui was mortally wounded in order to protect him. I'd totally hate myself if a supreme god died because of me. Plus I don't think you are over-doing that aspect of Oki which is quite cool.
As an Okami fan myself, I do drawings for Lunar New Year (Chinese/Asian New Year) greeting. You might find them interesting if you are into that kinda yearly greeting stuff.