A little bit of history about HND and how/why the slot system works... Some people don't seem to understand the process.
HND used to be the primary Tokyo airport. Due to its proximity to the city and increasing traffic, the air space was becoming congested and the normal airport noise complaints lead to Narita airport being built and the vast majority of long hurl flights were moved to NRT. HND became just domestic flights.
In 2007, HND started allowing limited international flights again, timed for what would become the night slot period, due to NRT being closed.
These flights were limited to "scheduled charter flights " to international destinations within the flight distance of the longest domestic flight (which meant Korea, Hong Kong and parts of China).
HND was the busiest airport in Asia prior to PEK and DXB bumping it from top spot.
A new intentional terminal and 4th runway was opened in 2010, which allowed an extra 30,000 flights/year (82 flights/day) during the international slot night period. The Japanese government allocated these slots out to nations for assignment to their airlines, Japanese airlines would get half of the slots to fly to those allocated nations. JAL can't get a slot meant for Germany and fly to Paris. They have to use that slot to fly to somewhere in Germany.
Due to the timing of the night slots, flight times and time zones, the slots lead to many of the North American and European flights to fail. (eg, a night slot at HND would require a midnight arrival/departure from JFK and midnight arrival at HND). The slot Australia has (that QF and NH use for SYD-HND) was allocated in this round.
In 2013 more HND slots were released, this time day slots, for use after the international terminal expansion opened in 2014. The US spent 3 years negotiating with Japan over this release because DL was making a big fuss about it and demanding enough HND slots to move their entire NRT hub. Australia didn't get any slots in this round.
Last year, the USAF handed back control over some airspace around the Yotoka Airbase, which combined with an expansion to T2 (ANA domestic) and new taxiways allowed for 50 additional day flights to be assigned. The US got most of these (24 flights with the normal 50/50 split to JP carriers). DOT recently finished assigning the 12 US carrier slots. and the remaining 26 slots were assigned by Japan last week.
The new taxiways and the international section of T2 are due to open when the new day slots become available for use. The international terminal is also being renamed to Terminal 3 at the same time. The airspace changes and airport expansion should allow for 271 daily international flights from next year (and almost 700 daily flights for NRT).
Australian and Japan have an open skies treaty, and while this means that Australian and Japanese carriers can fly unlimited flights/pax/cargo between AU and JP, HND is not part of Japanese open skies treaties.