I was looking for availability around mid-November. I've just tried searching again, and before it was only offering the a Qantas option. However, I have logged back in again, and it is showing SYD-MEL-NRT with JAL on the MEL-NRT leg, but no direct flight.

However, when I search for MEL-NRT to see if I can get the direct flight, it is only showing MEL-SYD-NRT with JAL on the SYD-NRT leg!!!

Fingers crossed it may just be the dates I have chosen, and more options may be made available nearer the time.