The poem signified a thawing in relations between the old enemies that can be traced back to Japanese Prime Minister Shinzo Abe's state visit to Beijing in 2018.

As Tokyo and Beijing stress that the state visit of Chinese leader Xi Jinping to Japan in April will not be canceled amid the coronavirus outbreak, a renewed focus is on how the world's second and third-largest economies could deepen ties.

Changing Chinese attitudes

Bitter territorial disputes and long-running grievances dating back to World War II have marred the Japan-China relationship for decades.

During WWII, the Japanese Imperial Army was responsible for a 1937 campaign of rape, murder and looting that became known as the Nanjing Massacre, in which an estimated 300,000 people died. Japanese air strikes during the war also inflicted severe damage on Chinese civilians in Chongqing, killing an estimated 32,000 people between February 1938 and August 1943.

China and Japan have often argued over how the past should be remembered.

Tensions flared in 2013, when the standoff over the disputed Diaoyu/Senkaku islands in the East China Sea inflamed nationalistic sentiment on both sides and impaired economic ties.

"This is the first step towards the improvement of the bilateral relationship based on the principle of the strategic mutually-beneficial relationship," Abe said after the meeting.

But while Chinese millennials with greater purchasing power are traveling more, the same can't be said of Japan, said Kudo. As the Japanese economy shrinks and millennials face issues such as the aging population and static salaries, there is less desire to explore the world, according to Kudo.

"You create an impression of another country by going there and making friends, but Japanese people aren't going to China that much, so they're forming their opinions based off of Japanese media reports," said Kudo.

Nevertheless, Japan is trying to make big-spending Chinese tourists feel welcome, erecting signs in Mandarin in Tokyo and broadcasting announcements in Chinese at train stations.

On a state level, things have been improving, too.

A 'marriage of convenience'

Nothing brings together two old foes like a common problem.

More recently, the rapprochement between China and Japan has had a lot to do with Trump's declaration of a trade war on China and Japan, according to Koichi Nakano, a political science professor at Sophia University.

"Before Trump's arrival, Xi and Abe didn't have such a good relationship, now their relations are more a marriage of convenience in face of the common threat," said Nakano.

But while Abe's support for China as it battles the coronavirus outbreak may have won him some mileage with Xi, it has sparked anger among his hawkish supporters at home, as Japan steps up efforts to contain its own outbreak.

"The Japanese government has taken relative soft stance when it comes to blocking the flow of people from China to Japan compared to some other countries," said Nakano. "Some of Abe's supporters were angry about that as they thought he prioritized his new friendship with Xi over national security."

Focusing on the positives

Despite this recent uptick in relations, fundamentally, Japan and China have rivaling visions for the future of the Asia-Pacific region and the role of China within it. Issues over territory have not gone away, but merely been placed on the back burner.

"The political elites have spent the decades vilifying either side to rally their troops behind the leaders, it would be naive to think that trend would change now," Nakano said.

While Japan needs to do business with China, it's not willing to sacrifice the umbrella of US military protection, and has already built up other allegiances across the region to counter a rising China, said Jeff Kingston, a Japan expert at Temple University.

"For now, both sides see an advantage in dialing down tensions. Some of the permafrost has thawed but there are still deep layers of frost -- and that's not just about territory, there is also historical differences," he said.

Compared to a century ago, China and Japan are now both highly modernized, globally significant economies, meaning any potential downturn in their relations could have serious ramifications globally.

"The recent outbreak has been a stress-test for bilateral relations, so taking what is anxiety-inducing and turning it around was clever," said Kingston. "That poem is trying to get people to listen to the better part of themselves."