TOKYO -- Aboard a Japanese survey vessel earlier this year, Tomomi Inada was roused from her berth in a commotion at 4 a.m. and told to look out of a porthole. The veteran Japanese ruling-party lawmaker was shocked to see the lights of a Chinese coast guard ship bearing down on her craft.
The coast guard ship's loudhailer crackled out warnings in Chinese, Japanese and English: Inada's vessel was in Chinese territory, it said, "Get out!"
"I was very angry to hear this," said Inada, a hawkish former defense minister, speaking to reporters in Tokyo a few weeks after leading a party of five conservative politicians on a rare trip to the Senkaku islands, a group of uninhabited islets in the East China Sea that Japan administers but China claims as its own. The April trip, by four members of Inada's Liberal Democratic Party (LDP) and one from the Japan Innovation Party, was the first known voyage there by Japanese politicians since 2013.
The eventful night for Inada and her party came amid mounting tensions playing out in waters across East Asia. As Beijing flexes its maritime muscle in the region and Washington and allies do the same, experts are voicing concern that the situation is developing into a tinderbox where a minor incident could flare into a serious international crisis.
While the Chinese presence did not deter the Japanese lawmakers from sailing close to the islets -- the government in Tokyo does not allow politicians to set foot on them due to political sensitivities -- the Chinese managed to jam the frequencies of some surveillance drones.
China is limiting its aggression to what is seen by analysts as a ''gray zone" short of actual conflict, but the latest Senkakus incident is part of a three-pronged maritime threat that is unnerving Beijing's neighbors. The increased hostility is currently focused on the Senkakus, Scarborough Shoal off the Philippines, and Taiwan's Kinmen islands.
All three island groups are claimed by China. The three locations are all in the so-called 'First island chain' -- a group of islands, including Taiwan, Okinawa and the Philippines, which is the first chain of major Pacific archipelagos off the East Asian continental mainland coast, and which China sees as its first line of defense.
The Senkakus, known as the Diaoyu Islands in China, have for decades been a source of friction between Tokyo and Beijing. Japan's Foreign Ministry says they are "an inherent part of the territory of Japan" and there is no issue of territorial sovereignty. Beijing says the islands are its inherent territory.
According to Japan Coast Guard data, China has been steadily sending more coast guard vessels into Japanese territorial waters and the contiguous zone around the Senkakus, prompting Tokyo to increase its own patrols. In 2023, a record 1,287 Chinese vessels operated in the contiguous zone on 352 days of the year, the Japanese data shows.
Last month, Japan said it had spotted Chinese ships near the islands for a record number of consecutive days.
"It is important to ensure that the situation in the East China Sea does not become like the situation in the South China Sea," Inada told reporters in Tokyo last month. "It is important to imagine a potential worst-case scenario, and it is very important to ensure that the government can take preparations for these different scenarios."
Stressing that she was not anti-China, Inada also spoke of the need to work with "like-minded" countries such as the U.S. and the Philippines to prevent Beijing from changing the status quo by force.
In a separate incident in April, a Nikkei Asia reporter was aboard a ship carrying supplies to Filipino fishermen working in the waters off Scarborough Shoal when a China Coast Guard ship fired water cannons at the boat after a flurry of early-morning radio challenges between the two vessels.
The crew, used to aggressive behavior by Chinese ships, laughed off the early volleys, which started around 9 a.m. But 50 minutes later, a steady barrage of water defaced the Philippine flag on the ship, with one person with experience in such confrontations saying the strength of the spray was "enough to bend steel."
The dousing continued for another couple of hours before the Filipino mission commander yelled, "Disengage! Let's disengage!" For some on board, the Chinese plan was clear: China came with the intent to kill.
The April 30 incident is a microcosm of the challenges Manila faces in protecting its territorial waters from China's ambitions to claim dominance over the disputed waterway. There have been at least four such incidents this year, following 10 confirmed by the Philippine Coast Guard in 2023. Earlier this month, the Philippine military denied a Chinese allegation that personnel had pointed guns at a coast guard vessel in May as Beijing seized supplies intended for a Philippine military outpost at Second Thomas Shoal.
Pointing to the warming of ties between Manila and Washington since President Ferdinand Marcos Jr. came to power nearly two years ago, Don McLain Gill, an analyst and lecturer at De La Salle University in Manila, told Nikkei Asia that Beijing "has illustrated a clear appetite for expansion and a disdain for U.S. influence."
Gill said China has managed to "exploit fault lines" within the region in past decades, citing examples such as Tokyo's previous reluctance to take a prominent role in regional security matters and Washington's "preoccupation away from the Western Pacific," a reference to conflicts in Ukraine and the Middle East.
"The ability of countries like the Philippines, Japan, and the U.S. to push for greater strategic cohesion in the South China Sea becomes a huge obstacle for China's expansionist ambitions, given the former's intent to secure the established order," Gill said.
Some Chinese commentators say that the growing tensions in the three areas are a result of the U.S. becoming increasingly provocative in expanding its military influence in the region.
The U.S. "is hyping up incidents" out of concern that China-U.S. naval and air encounters will get out of control, but also "out of political and diplomatic considerations, in the hope of exerting pressure or building momentum, and using public opinion and diplomacy to influence the situation," according to a March report on U.S. military activities in the South China Sea by South China Sea Strategic Situation Probing Initiative, a Beijing-based think tank.
At the recent Shangri-La Dialogue in Singapore, China's new defense minister, Dong Jun, hit out at the Philippines, saying that a "certain country, emboldened by outside powers," broke bilateral agreements and promises, and "made premeditated provocations."
But he saved his strongest barbs for Taiwan's ruling pro-sovereignty Democratic Progressive Party (DPP), accusing it of "erasing the Chinese identity of Taiwan" and pursuing "separation in an incremental way."
In the days following the swearing-in of Taiwanese President Lai Ching-te in late May, China conducted two days of "punishment" military drills around the democratic island. Communist China has never controlled Taiwan, but claims it as its own and has refused to rule out seizing it by force.
Beijing calls Lai a "separatist" and slammed his inauguration speech, in which he urged China to stop its coercion and aggression. Lai's center-left DPP supports alliances with major democracies instead of China.
Chinese coastal patrol boats in recent months have stepped up operations off the Kinmen archipelago -- Taiwanese territory that sits just a few kilometers from the Chinese coast.
Fears of an incident that could trigger a serious escalation are growing. In February, Chinese officials boarded a Taiwanese tour boat in the area for inspection. Beijing has since announced it would enhance maritime law enforcement and step up routine patrols in the vicinity of Kinmen and Xiamen, the Chinese city facing the islands.
This marks a break from the status quo that had held since the 1990s, when Taiwan's government set out "restricted waters" near its Kinmen and Matsu islands. For decades, Chinese and Taiwanese coast guard ships broadly kept to their own side of the boundaries.
China's stepped-up coercion around Taiwan's offshore islands, particularly Kinmen, should be seen within a larger picture of more aggressive behavior across the region, according to John Dotson, deputy director of the Global Taiwan Institute and a former U.S. Navy officer.
"Incidents around Kinmen beginning in February, involving fishing vessels and coast guard units, demonstrate how the PRC (People's Republic of China) will use 'opportunistic crises' in an effort to further erode Taiwan's de facto territorial sovereignty," Dotson told Nikkei Asia. "But it also fits into a broader pattern, connected with PRC pressure on the Philippines at Scarborough Shoal and Second Thomas Shoal."
"In the immediate term, the risk this poses of a significant crisis is low, but that risk will continue to grow over time," Dotson added.
Collin Koh, a senior fellow at the S. Rajaratnam School of International Studies in Singapore specializing in Indo-Pacific naval affairs and maritime security, said China has become increasingly belligerent since Xi Jinping came to power 12 years ago.
"A number of countries around the South China Sea, as well as Japan, are trying to avoid what is very likely a Beijing tactic to bait them into doing things that will provoke a huge backlash," Koh said. "These countries are trying to avoid even an accidental clash that could give rise to the Chinese escalations, using that as a pretext."
"The situation is both stable and unpredictable. It is stable because no one entertains the idea of going to war, but it is unpredictable because you will just need a spark, and then you will have a fire that will become uncontrollable."
Speaking back on dry land on a TV news show after returning from the Senkakus, Inada, now executive acting secretary-general of the ruling LDP, summarized her view on what her government's strategy should be: Japan "should quietly do what it needs to do, without letting its guard down," she said.
Additional reporting by Ramon Royandoyan in Manila, Thompson Chau in Taipei and Wataru Suzuki in Shanghai.