Japanese Foreign Minister Taro Kono arrived in Seoul on Wednesday for talks about a number of issues linked to the impending summit between North and South Korea.
The first such visit in more than two years comes at a time of frenetic diplomatic activity in Northeast Asia, ahead of the North's planned summits with South Korean President Moon Jae-in and US President Donald Trump.
Japan has largely remained on the sidelines, with suggestions last month of a third summit between Kim and Japanese Prime Minister Shinzo Abe quickly petering out.
Instead, Tokyo has found itself forced to rely on the US and South Korea to tackle its concerns regarding the North, which last year test-fired several missiles that flew over Japan, sparking security concerns.
Kono will meet with his South Korean counterpart Kang Kyung-wha on Wednesday morning.
As well as Pyongyang's "nuclear and missile issues", Kono has said he will try to ensure that "the abduction issue will be talked about in the North-South summit".
He was referring to Japanese citizens abducted by the North's agents in the 1970s and 80s in a bid to train spies in Japanese language and customs before overseas missions.
The North regularly condemns Japan over its brutal 1910-45 colonial rule of the Korean peninsula.
But ties between the South and Japan have also remained sour for years due to controversy over historical issues left unresolved -- including Korean women forced into sexual slavery for Japanese troops during World War II.
Seoul has urged Tokyo to take legal and moral responsibility, while Japan says that the issue was resolved when the two nations reached a controversial deal in 2015 to offer compensations to the victims.
Tokyo's top government spokesman Yoshihide Suga said "it is extremely important that Japan, the US and South Korea share information and coordinate closely" ahead of the two summits.
He said Japan's foreign minister would seek to boost a "forward-looking" bilateral relationship despite the row.
Kim is set to meet Moon on April 27 for a third-ever summit between the two neighbors, and is expected to talk with Trump in May or early June.
Japan -- a key Asian ally of the US and host of 50,000 American troops -- had long supported Trump's hardline position to press Pyongyang to abandon its widely-condemned nuclear and missile weapons programs.
But Trump's sudden decision to open dialogue with Kim reportedly stoked concerns over whether Japan was being ignored in the regional push to engage the unpredictable North.
Meanwhile, Chinese state media reported that a high-ranking Chinese diplomat plans to travel to Pyongyang later this week amid a flurry of diplomacy following Kim's surprise visit to Beijing last month.
Song Tao, who heads the ruling Communist Party's International Department, will lead an art troupe to Pyongyang on Friday to attend an arts festival, the Xinhua News Agency said.
It said Song had been invited by the International Department of the of North Korea's ruling Worker's Party. No details were given about any officials he would meet.
Kim met during his China trip with President Xi Jinping. It was his first visit since taking power six years ago, and was considered an attempt to repair traditionally warm ties with China that have deteriorated over the North's development of ballistic missile and nuclear weapons technology and China's enforcement of United Nations economic sanctions.
China is the North's most important trading partner, although trade has fallen drastically under the sanctions, taking a major toll on the country's ailing economy.
Kim's diplomatic moves could have a major impact on the direction the country takes in the months and possibly years ahead. Following his summit with Xi, Kim dispatched his foreign minister to Moscow, reportedly exploring the possibility of a summit with President Vladimir Putin.
China has long advocated a return to six-nation talks it hosted on the nuclear issue and appears anxious not to be sidelined by the North's new outreach to other players in that long-stalled process.
Song visited Pyongyang in November, becoming the last high-level Chinese official to do so.
