One of the biggest questions about US President Donald Trump's foreign policy in Asia is simply: what is his policy in Asia?

North Korea, sure.

Trade, well that's a broad topic.

What about the big-picture policy vision, following predecessor Barack Obama's "pivot" to Asia?

Those questions still largely remain, but here are a few things we learned from the Japan section of Mr Trump's trip.

Friends with benefits

Mr Trump is obsessed with being friends with world leaders — and telling us about it.

He mentions it over and over.

"Our relationship is extraordinary ... there has never been such a close relation between two countries, these two countries," Mr Trump said about his Japanese counterpart and occasional golfing buddy.

US President Donald Trump and Japan's Prime Minister Shinzo Abe vow to make their alliance stronger. ( Reuters: Jonathan Ernst )

Which may have made Japan's Prime Minister Shinzo Abe feel special, unless he read this description of Mr Trump's relationship with China's leader Xi Jinping.

"People say we have the best relationship of any president-president, because he's called president also," Mr Trump said last month.

Being friends is a no doubt a good start to global diplomacy, but there's more to a true friendship than repeatedly saying you like someone.

Leaders pile on 'massive pressure'

The new strategic policy on North Korea now appears to have a tag line: "Maximum pressure."

Both Mr Trump and Mr Abe used the term.

This is in distinct contrast to the Obama administration's policy of "strategic patience", which Mr Trump called weak and ineffective.

"So the President's strategy — and this strategy is in complete alignment with our allies, South Korea and Japan, and, increasingly, the entire world — is to maximise pressure," a senior administration official said in an on-the-record briefing to media on November 5.

"It is a diplomatic and economic campaign to maximise pressure on North Korea, to show — really to convince the leadership in North Korea that the one way out for them is to start reducing the threat and to move toward denuclearisation."

Japan's leader also dropped the phrase into his comments about Pyongyang.

"We must raise pressure to the maximum to create a situation in which North Korea comes to us and begs us to have a dialogue," Mr Abe said.

Of course, China is the country that can calibrate the pressure on North Korean leader Kim Jong-un, and it will be interesting to see what language Beijing uses when Mr Trump visits later this week.

Indo-Pacific, not Asia Pacific

The Trump administration is deliberately changing the way it describes the region we live in.

"We talk about an Indo-Pacific in part because that phrase captures the importance of India's rise," a senior administration official said during a briefing.

"It captures the importance of the maritime-free commons that allow our security and our prosperity to continue.

"And this is a region that includes China, it includes Japan, the Korean Peninsula, Northeast Asia. It includes Oceania, with our close partner, New Zealand and Pacific Islands, and our longstanding ally, Australia, in the south. India to the west; the United States the east."

Let's be clear, India was always part of "Asia Pacific", but the US now wants it in the title.

Mr Trump, however, used the term to imply some kind of policy blueprint for regional trade and security.

"And in partnership with the United States, the sovereign nations of the Indo-Pacific will work together to achieve a future of security, prosperity and peace," Mr Trump said.

"We will have more trade than anybody ever thought of under TPP [Trans-Pacific Partnership], that I can tell you ... TPP was not the right idea."

At the risk of stating the obvious, re-labelling the map isn't the same thing as a multilateral trade deal.

The Obama-era "pivot" to Asia is clearly long gone, but it's still unclear what will replace it.

US President Donald Trump finishes up the Japan leg of his 12-day Asia tour with Japan's Prime Minister Shinzo Abe. ( Reuters: Jonathan Ernst )

Jokes and pokes

Two world leaders, two gags, two very different results.

Mr Abe is not known as a funny guy, but he dropped some gentle humour into his speech at a press conference on Monday.

Speaking about playing golf with Mr Trump (who is a good golfer, although perhaps not as good as he claims) and Hideki Matsuyama (ranked 4th in the world), Mr Abe said that while they didn't keep score, he thought it was neck and neck.

His wry half-smile made the line work even better.

US President Donald Trump fist pumps Japan's Prime Minister Shinzo Abe during a round of golf. ( Reuters: Japan's Cabinet Public Relations Officer via Kyodo )

By contrast Mr Trump appeared to go off-script with a compliment that immediately lurched into a sneering insult.

"The Japanese people are thriving, your cities are vibrant, and you've built one of the world's most powerful economies," Mr Trump said.

Turning to Mr Abe's podium, he continued.

"I don't know if it's as good as ours, I think not. OK? And we're going to try to keep it that way, but you'll be second."

It made Mr Trump appear like a bully and Mr Abe had no choice but to smile through it.

It was not the intended ending to the buddy movie that the US President had been pitching hard for his two days in Japan.