TOKYO - The summit talks on Tuesday (June 12) between US President Donald Trump and North Korean leader Kim Jong Un will have an extensive impact on how Japan assesses and recalibrates its national security policy, going far beyond the strategic environment in and around the Korean peninsula.

Japan is deeply concerned because recent rapid developments leading up to the summit have left Tokyo sidelined from the process despite its high stakes in the outcome of the summit.

Japan has been one of the members of the Six-Party Talks for North Korean nuclear weapon issues. However, while all the other four member states - South Korea, the US, China and Russia - have had or are scheduled to have direct summit talks with North Korea, only Japan has been excluded from this de facto series of bilateral talks with Mr Kim.

Furthermore, Japan has been spearheading the multilateral efforts to apply maximum pressure on North Korea only to have this unravel following Mr Kim's launch of his "smile offensive" at the time of the Pyeongchang Olympic Games in February and South Korean President Moon Jae In's decision to play along with it.

Now that Mr Trump is to meet Mr Kim, Chairman of North Korea's State Affairs Commission, Prime Minister Shinzo Abe has scrambled to make sure that Japan's voice is heard and its specific interests considered.

Mr Abe's greatest concern is the abduction issue, which he has made his "highest priority". The Japanese government believes there are still a number of its citizens who were abducted by North Korea and are still being held there.

Among all the abductees, only five were returned to Japan in 2002, but since then progress in negotiation to get back the rest has stalled, to the greatest disappointment of the families of the abductees and Japanese public.

Mr Abe seems to think that the Trump-Kim meeting could be the best and perhaps the last chance to regain the momentum to resolve this issue on his watch.

Mr Trump promised Mr Abe at their meeting last week that he would raise this issue at the summit with Mr Kim. While this must have been a relief for Mr Abe, it does not guarantee any positive response from Mr Kim. North Korea has insisted that the abduction issue has been settled and has criticised Japan for raising it.

It would appear that Mr Kim intends to make use of the abduction issue to drive a wedge between Japan and the US and to extract maximum economic aid from Japan.

What it boils down to is that even if Mr Trump raised it at the summit, any further movement will depend on talks between Mr Abe and Mr Kim. Mr Abe has expressed a willingness to hold direct talks with Mr Kim, but has not had any positive response.

The second major concern for the Abe government is that short- and medium-range missiles will be set aside from the agreement on ballistic missiles between the US and North Korea.

While it is understandable that the US would want to focus on North Korean inter-continental ballistic missiles (ICBMs) that can reach targets in the US, what worries Japan more are the shorter range missiles.

Japan is within the range of 200 to 300 North Korean No Dong missiles, intermediate-range weapons that are believed to be capable of delivering both conventional and nuclear warheads.

If Mr Trump chose to apply his "America First" approach and settled only with the freezing of further development of ICBMs, Japan could be left alone with the existential missile threat from North Korea. Such an outcome would severely undermine the credibility of the US-Japan alliance, making a decoupling more likely.

The final, and most serious, strategic concern for Japan is whether the summit can overcome the chronic deadlock over the denuclearisation of North Korea.

The history of all negotiations with North Korea thus far suggests that Pyongyang would go as far as suspending or freezing the on-going development of its nuclear capabilities, but will stop short of dismantling any part of its existing inventory of nuclear weapons.

What is more, it will walk away with all the "rewards" gained through its promises of future dismantlement undertaken in its preferred "phased approach" towards denuclearisation.

The question is whether Mr Trump can break away from this suspension/dismantlement trap. The only way to avoid it is to frontload dismantlement. In other words, to lock in as much as possible the dismantlement of nuclear weapons at the start of the process, not at the end. If Mr Trump cannot achieve this goal, this historic summit may well end up as yet another failed attempt.

The result of these denuclearisation negotiations can have a serious impact on the strategic thinking of Japan.

Japan's sense of nuclear security stands on two pillars: the Non-Proliferation Treaty (NPT) and the protection offered by the US' extended deterrence. It is fair to say the NPT regime has already been crumbling. There are a number of nuclear states that have not joined this treaty, including Israel, India and Pakistan. North Korea was once a signatory but withdrew from the treaty in 2003.

Another failed attempt of North Korean denuclearisation this time around could be a nail in the coffin of the NPT regime as seen from the Japanese perspective. Failure could also weaken Japan's faith in the US' reliability as a treaty ally.

The perception of potential attacks that Japan may sustain from North Korea has fundamentally changed over the past few years. It used to be based on a "spill-over" scenario, in which Japan may suffer armed attacks from North Korea as a spill-over of a war that breaks out on the Korean peninsula.

But now Japan and the Japanese people are fully aware that they could be the first to get hit because of the advanced missile capabilities of North Korea and its possible change of strategy. As a matter of fact, some of the recent table-top exercises conducted by multiple think tanks, including those of Japan, the US and South Korea, had scenarios that involved isolated nuclear attacks on Japan.

Japan now regards itself as a "frontline state" that is located in the unified "theatre" with the Korean peninsula. This concern is another reason why Tokyo believes that it should be included in the multilateral talks on the North Korean missile/nuclear weapons issue and is frustrated with how the current situation is playing out.

It is also why the result of the Trump-Kim talks is being closely watched by Japan as it could lead to a fundamental rethink on how it intends to defend itself.

Yoichi Kato is Senior Research Fellow at Asia Pacific Initiative, a Tokyo-based think-tank.