The stepping down of Michael Flynn from his role as U.S. national security adviser earlier this week represents a blow for Japan because he was predicted to become an effective intermediary between the two countries.

Flynn's resignation -- which took place immediately after U.S. President Donald Trump and Prime Minister Shinzo Abe's "golf diplomacy" summit over the weekend -- symbolizes the instability of the Trump administration. But this could just be the start. A senior Japanese government official said, "Events such as this might continue to happen."

Notably, former security adviser Flynn was present at both of the recent meetings between Trump and Abe -- one held inside Trump Tower in Manhattan in November 2016, and the summit meeting carried out in the White House on Feb. 10.

In Japan, it was expected that Flynn would become a key person in terms of Japan-U.S. security policy. This is why the Japanese government made a conscious effort to develop a relationship with Flynn, even before Trump was elected president in November 2016.

In October 2016, before the U.S. presidential election had even taken place, Flynn visited Japan and took part in unofficial talks with Japan's Chief Cabinet Secretary, Yoshihide Suga. In addition, in December 2016, Shotaro Yachi -- National Security Adviser to the Prime Minister of Japan -- made a visit to Washington D.C., and held talks with Flynn. Subsequently, the pair continued to deepen their relationship after Yachi's visit.

According to a source close to the government, Flynn -- who understands the significance of the Japan-U.S. relationship -- had a major influence on the joint statement made by Trump and Abe in Washington on Feb. 10, which was critical of China's military expansion as well as North Korea's nuclear weapon and missile development.

While Flynn's resignation represents a loss for Japan, it was perhaps not that much of a surprise. It is thought that the Prime Minister's Office knew in advance that Flynn would resign.

As U.S. Secretary of Defense James Mattis now takes the lead in terms of U.S. security policy, Japan is putting on a calm face. For example, at a press conference on Feb. 14, Suga vowed that, "Flynn's resignation will not have an effect on practical day-to-day matters."

However, given that the government is keen to progress with negotiations with Russia regarding joint economic activity in the Northern Territories, there is an element of uncertainty as to how Flynn's resignation will affect the relationship between the U.S. and Russia.