King Salman and hundreds of business leaders from Saudi Arabia are in Japan for talks today mainly expected to focus on economic ties.
The visit is the first by a Saudi king in 46 years, though Salman visited more recently as crown prince.
Saudi Arabia is one of Japan's biggest suppliers of crude oil, accounting for about a third of its total imports of oil from the Middle East.
The kingdom is striving to diversify its economy away from its heavy reliance on oil exports, and Salman is on a month-long tour of Asia to advance his kingdom's economic and business interests.
Japan's Chief Cabinet Secretary Yoshihide Suga told reporters today that Japan is willing to provide support for the economic power in the Middle East.
"We will discuss growth strategy, including our 'Saudi Vision' project," he said, referring to Japanese collaboration with Vision 2030, a roadmap adopted by the kingdom last year for its development and economic objectives.
He did not confirm reports that the countries would agree to set up a special economic zone in Saudi Arabia.
Salman met with Japanese Foreign Minister Fumio Kishida and was to meet Prime Minister Shinzo Abe later today.
Reports say Japan plans to urge that Saudi Aramco, the state-run oil company that is being partially privatised, seek a share listing on the Tokyo Stock Exchange.
Separately, Saudi Arabia's sovereign wealth fund and Japanese telecoms provider and energy company Softbank have joined forces in setting up a USD 25 billion private fund for technology investments.
Trade between the countries fell overall last year as oil prices dropped. Japan's 2.1 trillion yen (USD 18.6 billion) in imports from Saudi Arabia in 2016, mostly oil and gas, dwarfed its exports of 546.3 billion yen (USD 4.8 billion).
The delegation arrived late yesterday on about 10 aircraft. Officials said top hotels and car hire services would be busy handling the unusually large group during its four-day visit.
Salman's stop in Japan follows visits to Indonesia and Malaysia. He is due to travel on to Brunei, China and the Maldives.
While seeking investment and help with Saudi industrialisation and development of its services sector, Salman has also offered help.
Earlier, he pledged USD 1 billion in development finance for Indonesia and closer cooperation for combating transnational crime such as human trafficking, terrorism and the drugs trade.