The historical rapprochement between China and Japan, the world's second- and third-largest economies respectively, is one of the most pivotal events for Asia in 2018 — second only to the "Cold War" on the Korean Peninsula prospectively coming to an end. 

On Friday in Beijing, Japanese Prime Minister Shinzo Abe spoke about a shift from "competition to cooperation" as China's Premier Li Keqiang said the relationship was lifted to a "new phase of cooperation."

As with North Korea, there are legitimate concerns about China's sincerity in expanding cooperation. Even if this change of heart from Beijing is simply a tactical maneuver, Tokyo will have to take a leap of faith. Both countries are responding to the changing landscape in East Asia. The post-Second-World-War "pax Americana," symbolized by US troops in Japan and South Korea, could be coming to an end. This has loosened up the rigid balance of power in the region.

Friends in hard places

However, the concrete reason underpinning this Sino-Japanese détente is the trade war being waged by US President Donald Trump and the tariffs slapped on Chinese goods. The US government is also becoming more concerned about political and military issues vis á vis China.

In this situation, China needs new friends. The charm offensive from Beijing is a way to keep Tokyo from joining Washington's strategy of isolation.

Chinese President Xi Jinping surely has not given up his reservations about Shinzo Abe. The Chinese president sees Abe as a revisionist, who wants to gloss over Japanese crimes during World War II. Abe has pursued a more aggressive Japanese foreign policy, strengthening Japan's military for the first time in decades and opposing China's hegemonic claims in the region.

Despite these thorny issues, China's leaders can no longer ignore Abe. Along with Angela Merkel's Germany, Abe's Japan has become an important advocate for global cooperation.

Japan demonstrated this when it stayed on with the Trans-Pacific Partnership (TPP) trade agreement and played a major role in renegotiations after the US abandoned the deal. And the accelerated completion of the free trade agreement with the EU highlighted Abe's strong advocacy for open markets.

Caught in global rivalry

Japan fears heavy collateral damage if it becomes swept up in the growing US-China rivalry. China is Japan's most important trade partner, an important sales market and a major production center. Abe has been pushing for better relations with China for years, partly because of pressure from Japanese businesses.

With this latest reset in the relationship, Japan is recognizing China's rise as an economic giant. This is exemplified by the planned end of Japanese development aid to China, which began 40 years ago under the Treaty of Peace and Friendship. This is a gesture of fairness and equality from Japan, which, up to now, has often treated China with condescension.

Read more: China accuses Japan of 'playing with fire' in South China Sea

If the spirit of this week's summit continues, it would be a boon for peace and prosperity in Asia. The danger of military conflict erupting over Japan's Senkaku islands, claimed by China as the Diaoyu islands, has also been diminished as both sides want to set up a hotline. Neither side is giving up their territorial claims, but they are cleverly putting them aside for now. 

Read more: Maritime hotline hints at warming Tokyo-Beijing ties

Cooperation on infrastructure projects is another promising development. Instead of bidding against each other on contracts, China and Japan can now work together, for example, on building high-speed rail systems in Thailand, Indonesia and elsewhere in the region.

Chinese cooperation with Japan on infrastructure means that rail lines, highways, airports and container ports will be built with better quality, fairer financing and more respect for environmental norms. These things have previously been ignored by China.

With this in mind, the nearly 50 agreements proposed by Beijing on projects and finance mechanisms are a sign of hope.

This rapprochement between China and Japan may not be a "historic turning point," as Abe said during the summit. But the thawing of relations is a starting point for big changes that could have far-reaching significance.