I don't quite know how to say it right. You have nice graphics and a nice mood and a nice setup, but why am I throwing sushi? Does it get any cheaper if you throw it on others people's plate? More importantly: How do I throw sushi? Aiming at the food and picking things up is the hardest part. I think it would be better if you could just tap on the sushi, the sushi starts floating in front of you and then you flick it with a swipe.
That way it could be a really addictive casual game.
Also, the other customers could kind of react on you throwing sushi at them.