It should come with the Japanese sweet.
You should ask for whatever you want, and there should be no problem.
That said, I did LAX-NRT-SIN and back a few months ago and got the "I'll have to see if it is possible" and "I'll see if I can do that" excuses when I asked for caviar and the western dessert, having ordered the Japanese meals on all sectors.
In the end, I got whatever I asked for. But a few of the FAs did not seem, well, pleased with the request.
They have to throw away any food that's "left over", just remember that and don't feel too bad about telling them what you want.