TOKYO — Japan, like the rest of the world, was taken by surprise by news of Kim Jong Il's death.
And as an historical nemesis of the communist state, it has as much reason as any to fear a destabilizing power struggle in Pyongyang or the emergence of a young Kim even more belligerent in tone and deed than his father.
Within hours of the announcement of Kim's death, Japanese officials voiced hope that the handover of power in the world's only communist dynasty would not complicate pressing regional concerns, not least North Korea's nuclear ambitions.
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"The Japanese government hopes that this unexpected development will not have a negative impact on peace and security on the Korean peninsula," the chief cabinet secretary, Osamu Fujimura, told reporters.
The prime minister, Yoshihiko Noda, cancelled what was to be his first speech since taking office in early September and convened an emergency meeting of security officials.
The country's self-defense forces and coastguard were told to step up surveillance in waters dividing Japan from the Korean peninsula.
But as is so often the case when North Korea takes the world by surprise, Japan said little of substance until it had spoken to its closest ally, the United States.
That consultation, between the US Secretary of State Hillary Clinton and Japan's foreign minister, Koichiro Gemba, produced a predictable united front on Washington yesterday.
"We both share a common interest in a peaceful and stable transition in North Korea as well as ensuring regional peace and stability," Clinton told reporters in Washington.
Japan, which has no diplomatic relations with the North, is part of the stalled six-party talks on North Korea's nuclear weapons program, and has joined international sanctions imposed in an attempt to pressure the regime into ditching its nuclear ambitions.
North Korean has previously sent ballistic missiles over Japanese territory during tests of its rocket technology, and rattled nerves in Japan with its nuclear tests in 2006 and 2009.
Japan's part in the negotiations has been complicated by its additional demand for a resolution of the North's Cold War abductions of Japanese citizens, who were used to train communist spies.
Kim Jong Il returned five of the abductees to Japan following a meeting in Pyongyang with the then Japanese prime minister, Junichiro Koizumi, in 2002.
Japan, however, says the regime has yet to offer satisfactory explanations about the fate of at least a dozen more of its citizens. Pyongyang insists that eight of them had died, while others were never abducted.
Kaoru Hasuike, one of the repatriated abductees, said in a statement after Kim's death: "I hope the Japanese government will carefully analyze the state of affairs in North Korea and do its best to secure the safety of abductees still left there."
Professor Hajime Izumi, a Northeast Asia specialist at Shizuoka University, said it was too early to tell whether Japan should be alarmed by the new regime in Pyongyang.
"We have no idea how Kim Jong Un will run the state, whether or not he will devise his own foreign policy," Izumi told GlobalPost. "Japan was clearly shocked by the news, but its response, to prepare for all contingencies, was appropriate."
North Korea's relations with Japan, as with the rest of the region, will be determined by its nuclear ambitions.
"The most serious threat to Japan would be if North Korea were to stick with its nuclear weapons program and continue to build its own light water [nuclear] reactors and enrich uranium," Izumi said. "It already has missiles capable of reaching Japan, so the ability to arm them with nuclear warheads would pose a grave threat."
There are causes for guarded optimism, however. Plans for a meeting between Japan, the US and South Korea could signal a willingness to kick-start six-party nuclear talks, which haven't been held since 2009.
At present, North Korea must meet preconditions for the talks to begin again — an end to uranium enrichment and a start to denuclearizing — but Izumi suggested concessions could be possible.
"We have to think about the best way of promoting a prudent and non-confrontational North Korea through the six-party talks," he said. "One possibility is to revive them without preconditions."
Japan's announcement on Tuesday that it will replace its aging fleet of fighter planes with 42 US-made stealth fighters is seen as further evidence of concerns over North Korea.
"The security arrangement surrounding future fighter jets is transforming," the defense minister, Yasuo Ichikawa, told reporters. "The F-35 has capabilities that can firmly respond to those changes."
Those concerns are well-founded, says Poornima Subramaniam, an Asia-Pacific analyst at IHS Jane's in London. She warned of a possible repeat of the 2010 surprise attacks on the Cheonan and Yeonpyeong island, or the "considerable risk of accidental clashes, considering the militaries of both North and South Korea are likely on emergency alert status."
But, she added, the possibility of conflict in the region "appears unlikely as North Korea appears to have been preparing for this succession since 2008, when Kim-Jong Il's health condition deteriorated. More likely is a period of calm as its military resolves its new internal power structures."