The Government of Japan supports the exclusive use of the term “Sea of Japan”, while the Republic of Korea (ROK) prefers to term "East Sea”. Below is an overview of some official stances on the matter.
The United Nations
In 1992, South Korea first brought up the name debate at the Conference on the Standardization of Geographical Names. It was brought up again many times over the years, although the United Nations consistently maintained that the UNCSGN was not the appropriate place for the matter to be determined. In 2004, the United Nations informed the Japanese government that “Sea of Japan” was to be used in all UN official documents.
The International Hydrographic Organization (IHO)
As of 2012, the International Hydrographic Organization uses only the term “Sea of Japan”. The debate is eligible to be renewed in 2017.
The United States Board on Geographic Names (BGN)
The United States Board on Geographic Names advocates for the term “Sea of Japan”. The CIA’s World Factbook follows these guidelines.
The Government of the United States of America
On June 29, 2012, the Assistant Secretary of State For East Asian and Pacific Affairs released the following statement:
It is longstanding United States policy to refer to each sea or ocean by a single name. This policy applies to all seas, including those bordered by multiple countries that may each have their own names for such bodies of water. Concerning the body of water between the Japanese archipelago and the Korean peninsula, longstanding U.S. policy is to refer to it as the "Sea of Japan".
The quote goes on to say the following:
"U.S. usage of the 'Sea of Japan' in no way implies an opinion regarding any issue related to sovereignty."
In the U.S. state of Virginia, legislation requires textbooks to use both “Sea of Japan” as well as “East Sea”.
The National Geographic Society
The Manual of Style of the National Geographic Society states that “when scale permits, Geographic maps show the alternative name East Sea in parentheses after Sea of Japan."