ok first off, who decided on using a Japanese fish on a Chinese restaurant. Koi Carp were initially bred in Japan.
Berry, koi (well the 'nishikigoi' anyways as koi means carp in literal Japanese translation

) have a fair amount of importance in japan (can't remember exactly why off the top of my head thoygh). However ....... Wiki says: in Japanese, 'koi' is a
homophone for another word that means 'affection or love'; koi are therefore symbols of love and friendship in Japan.
So I suppose you could say its implying a friendly atmosphere and you'll love the food.
EDIT: it looks like China use the koi as a new year symbol for prosperity.
As to the design, personally I think its more Japanese than Chinese, the koi plus the shape of the building are more synonymous with Japan to me (I like Japanese culture a fair bit so I've probably picked up more than the usual customer would though

). Chinese buildings have more of a 'flick' to the end of the roof compared with Japan.
If you were to take it forward I would say try a darker shade of red on the koi, there are some really deep warm reds used in some oriental arts which I reckon could work better than the bright red.
I prefer the brown building too over the black one.
I'm also going to raise the question of hows it going to be used (it might have been mentioned but I havent seen it), theres a lot of colours etc going on so it could have some consequences further down the line.