Illustration: Liu Rui/GT

After the arbitral tribunal in The Hague issued the award on the South China Sea initiated by the Philippines on July 12, what surprises China is that the US, which was behind the farce, acts in a calm manner, while its ally Japan took a high-profile stance.

Before the award was issued, Japan imposed pressure on ASEAN members to support the award. After the award was announced, it even held maritime law-enforcement exercises with the Philippines. At the Asia-Europe summit on Saturday in the Mongolian capital Ulan Bator, Japan tried to highlight the South China Sea issue in the joint statement.

Why has Japan responded so actively? First, during the Upper House election earlier this month, the Liberal Democratic Party-led ruling coalition won two thirds of the votes, which means the rectification of the pacifist constitution will be brought to the table soon.

Given constraints from domestic opposition forces and doubts from the international community, hyping up the tense situation in the South China Sea will divert the attention of the international community and bolster the legitimacy of constitutional revisionism within the country.

Meanwhile, Japan has taken control of China's Diaoyu Islands and worries that China will take it back. The more chaotic the South China Sea is, the more strategic attention China has to pay to it. Japan is keen to see such a scenario as it can ensure its actual control of the Diaoyu Islands.

Maritime disputes still exist between China and Japan over the East China Sea. Japan may have drawn a lesson from the South China Sea arbitration and plans to resort to the same approach to frustrate China's oil and gas activities in the East China Sea.

China's oil and gas exploitation activities are conducted at the Chinese side of the "middle line." China has shown restraint as it demands the disputed territory fall within the outer edge of the natural prolongation of its continental shelf rather than the "middle line."

If Japan resorts to arbitration over the East China Sea, it may fall into its own trap. Given the award in the South China Sea arbitration, the Okinotorishima rock, which Japan claims is an island, will be defined as a rock, and thus does not fall within its Exclusive Economic Zone (EEZ).

We may draw the conclusion from Japan's actions that international law is merely a tool that serves Japan's national interests and to contain China in the South China Sea.

Japan will play a more aggressive role in the aftermath of the South China Sea arbitration. As the term of US President Barack Obama, who advocates a rebalance to the Asia-Pacific strategy, comes to an end, Washington may adopt a conservative attitude toward East Asia. The White House's East Asia strategy will be decided by the next administration. During this vacuum, a more high-profile Japanese diplomacy suits the interests of both Japan and its American ally.

Japan has a long-standing friendship with new Philippines President Rodrigo Duterte. Duterte was mayor of the southern city Davao where the Japanese have exerted a profound influence. After winning the election, Duterte first met with the Japanese ambassador. Japan is expected to fully exploit these long-standing ties.

It is interesting to note that while Japanese Prime Minister Shinzo Abe hyped the South China Sea issues at the Asia-Europe summit, he also expressed willingness to improve relations with China. This reflects Japan's bottom line of not ending up deadlock with China. It would rather push the Philippines and even Vietnam to the forefront to make them serve its own interests.

As neighbors and major East Asian powers, China and Japan should cooperate and maintain regional order. It is normal for them to have divergences and competition. But Japan's gap between words and deeds can hardly win trust from China or do good to the regional order.

The author is a research fellow at the Institute of International Relations, Shanghai Academy of Social Sciences. opinion@globaltimes.com.cn