Iranian President Masoud Pezeshkian discussed the developments after a ceasefire with the US in a phone call with Japanese Prime Minister Sanae Takaichi.
Takaichi also "agreed to keep communicating with" the Iranian president, Kyodo News reported.
Ahead of the phone call, Japan had welcomed the ceasefire, calling it a "positive move."
Tokyo had been arranging the high-level talks amid the US-Israeli war with Iran, which stopped early Wednesday after Pakistan, the mediator between Tehran and Washington, said the two sides had agreed to halt fighting along with their allies in the Middle Eastern region.
Pezeshkian and Takaichi "are believed to have discussed the immediate ceasefire agreement between the United States and Iran, as well as efforts to calm tensions in the Middle East," the report said, citing sources.
Takaichi also called on Tehran to "swiftly secure safe Hormuz passage." Japan is highly dependent on energy sources from the Middle East, from where it procures some 90% of oil and gas.
It released energy sources from its strategic reserves twice.
Pakistan, the mediator of indirect talks between the US and Iran, announced the two-week ceasefire. Many countries have welcomed the ceasefire.
US President Donald Trump said he agreed to halt strikes, contingent on Iran reopening the Strait of Hormuz "completely, immediately, and safely."
Tehran imposed control over the Strait of Hormuz after the US and Israel initiated war on Feb. 28, with Iran allowing only vessels of "friendly countries."
US President Donald Trump had urged Japan, a key ally of Washington in the wider Asia-Pacific region, to deploy its naval assets to the Gulf. Tokyo did not.
Regional escalations raged when Israel and the US launched an offensive against Iran on Feb. 28, killing more than 1,340 people, including then-Supreme Leader Ayatollah Ali Khamenei. Iranian authorities have not updated the toll in recent days.
Iran retaliated with drone and missile strikes targeting Israel, Jordan, Iraq, and Gulf countries hosting US military assets, causing casualties and damage to infrastructure while disrupting global markets and aviation.
At least 13 US servicemen were killed and dozens of others wounded during the conflict.
