ScoMo's visit to Japan comes at a time when Australia-China relations are at a low point and there is uncertainty in the United States over its transition of political leadership.

That unpredictability is bringing Canberra and Tokyo together, with the nations planning to strengthen business and defence ties. But it is unclear whether a long-negotiated key military cooperation agreement will be signed on this trip.

The subject of a travel bubble between Australia and Japan has been complicated by fears of a third wave of coronavirus cases in Japan.

The country had a record number of infections in the past week.

But much of the focus will be on defence and maritime security.

Over the past few years, the defence relationship between Japan and Australia has grown stronger, with bilateral air combat exercises above Japan's northern island as well as naval exercises with the US in the South China Sea.

You do not have to look hard to see how Australia-Japan ties have improved in the past few months.

Japan's new Prime Minister, Yoshihide Suga, picked Morrison for his first call as the country's new leader, ahead of US President Donald Trump, the leader of Japan's closest ally.

Last month, Foreign Minister Marise Payne and Defence Minister Linda Reynolds both visited Tokyo within weeks of one another for meetings with their Japanese counterparts.

As it did in those meetings, China and its increasing assertiveness is certain to dominate private discussions between Suga and Morrison — though it will be a surprise if the leaders mention this by name.

Expect it to be framed by language about the "rules-based order" and the "free and open" or "peaceful and prosperous" Indo-Pacific.

Japan's 2020 Defence White Paper contained more criticism of China than ever before — particularly over Beijing's "relentless" unilateral attempts to change the status quo in the region by coercion around the Senkaku Islands.

The islands are controlled by Japan but claimed by China, which has been sending its Coast Guard ships into Japan's territorial waters.

Australia's economic challenges with Beijing are growing by the day, with sanctions being placed on many products.

News about the increasing Chinese sanctions is also being reported in Japan.

Stronger defence ties held up by rules on ADF operating in Japan

In the past few years, Australia and Japan have signed intelligence and defence research-sharing agreements.

But a sticking point in the Japan-Australia defence relationship has been a document known as the Reciprocal Access Agreement (RAA).

The document sets out what's required for Australian Defence Force (ADF) troops to legally operate in and around Japan, and the same for Japan's Self Defence Forces in Australia.

During a speech at the Australian embassy in Tokyo in 2018, Australian National University professor John Blaxland described the RAA as akin to a status of forces agreement.

"It expedites and facilitates rapid and seamless interoperability and ADF elements in Japan, or wherever we might be based, in response to a crisis like the Indian Ocean tsunami or typhoons in the Philippines," he said.

"[There was the] Fukushima disaster in Japan where Australian C17 [aircraft] flew in equipment but struggled to get it off boarded because of administrative procedures that had not been agreed upon beforehand."

But talks on the deal have been stalled over the condition of Australian troops being subject to the death penalty in Japan.

The Japan-US Status of Forces Agreement implemented after World War II has been a historical source of tension between Tokyo and Washington DC, so there's some degree of caution being applied here, according to Carnegie Endowment senior fellow James Schoff.

Schoff is a former senior US Department of Defence East Asia specialist.

"There were plenty of cases where crimes that were committed [by US troops] where suspects were not handed over within 'X' number of days — in some cases never handed over," he said.

"[There was a] 'We'll take care of it, don't you worry kind of thing,' and that led to real public political dissatisfaction in Japan with the way that is."

That makes it politically sensitive in Japan, but the ABC understands there is broad agreement on the text of the document, subject to any last-minute legal changes.

It may not be signed today and it's unclear whether Australian troops will be subject to the death penalty if they are acting outside of their official duties.

Japanese media have reported they will "be tried under Japanese law".

As the Foreign Minister visited last month, Australian negotiators were locked in discussions for weeks, trying to desperately make progress on the agreement ahead of this planned visit.

Many Australian ministers and prime ministers have come to Japan indicating a deal was close. In 2019 then defence minister Christopher Pyne toured a Japanese ship, expecting a deal would be signed in the first quarter of that year.

It was not.

So unless the document is signed, it's something worth keeping in mind.