Japanese Prime Minister Kishida Fumio and South Korean President Yoon Suk-yeol have shared the recognition that moves to improve bilateral relations are back on track.

This came during their summit in Seoul on Sunday. It marks the first full-fledged resumption in 12 years of mutual visits by leaders of Japan and South Korea.

Kishida and Yoon welcomed the restart of what they call "shuttle diplomacy" less than two months after the South Korean president visited Japan in March.

The leaders confirmed that they will strengthen bilateral and trilateral security cooperation among Japan, South Korea, and the United States in light of North Korea's nuclear and missile programs.

On a wartime labor issue, Kishida told Yoon that his government remains unwavering in inheriting the positions of previous Cabinets on historical perceptions.

Kishida also touched on the issue at a joint news conference after the meeting. He said he is heartbroken that many people endured significant suffering and sadness under the harsh environment at the time.

The Yoon administration is believed to see this remark as a certain concession from Japan.

Yoon stressed that his government will faithfully implement a plan it announced in March to settle the issue.

The plan involves having a government-affiliated foundation pay damages in place of Japanese companies to plaintiffs who say they or their families were forced to work for the firms during World War Two.

Kishida emphasized that his duty as Japanese prime minister is to join hands with South Korea in a future-oriented manner while taking history and related developments into consideration.

Kishida will likely try to mend and develop bilateral ties through summits and various other forms of dialogue. Japan has invited Yoon to the Group of Seven summit set to begin in the Japanese city of Hiroshima on May 19.

Yoon said he will meet the leaders of Japan and the US in a tripartite meeting on the sidelines of the G7 summit. He is apparently seeking to further cement trilateral unity to counter North Korea's nuclear and missile programs.

Yoon also said he and Kishida agreed Seoul will send a team of experts to inspect the Fukushima Daiichi nuclear power plant this month in connection with Tokyo's plan to release treated and diluted water into the ocean.

The power plant in northeastern Japan suffered a triple meltdown in the March 2011 earthquake and tsunami.

Water used to cool molten fuel mixes with rain and groundwater. The water is treated to remove most of the radioactive materials before being stored, but it still contains tritium.

The treated water will be diluted to reduce tritium levels before it is released into the ocean. Its tritium concentration will be lowered to one-seventh of the World Health Organization's standards for drinking water.