This topic got me thinking as to why QF would be struggling, with only two airlines on the routes.
One thing I could think of is that it is mainly a business and tourism customers, and not too many visiting friends and relatives. Where I work is quite large and has a number of people from different cultures. The main ones would be Chinese (both from China and Chinese/Singaporean), Indian and then the Aussies with a European background. Out of about 700 people there are only 3 Japanese.
I don't have immigration figures, but if this is indicative of the rest of the population this could be one of the reasons why Japan is a difficult market. Business travel is pretty constant and tourism can be fickle, but the visting friends and relatives seems to be a small pool of people to rely on to travel.
These are just my thoughts on one of the reasons. Of course you have also got QF trying to milk the most cash possible, by offering next to nothing.