From now on, I will tell you why it should be marked as 'Donghae'.
The East Sea area is adjacent to four countries, South Korea, North Korea, Japan, and Russia, and is especially composed of the territorial waters of these countries and the Exclusive Economic Zone (EEZ).
This means that in the East Sea waters, various countries share'jurisdiction' or 'sovereign rights'.
The geographical name for a feature shared by two or more countries is generally determined through consultation between the countries concerned, and if there is no agreement on the name of the feature, the place name used by each country is included.
These general principles of mapping are also confirmed by the resolutions of the International Hydrographic Organization (IHO) and the United Nations Conference on the Standardization of Geographical Names (UNCSGN).
In addition, the East Sea area falls under the 'semi-closed sea' stipulated in Article 122 of the UN Convention on the Law of the Sea.
In accordance with the general principles of mapping and related resolutions above, the Korean government has initiated bilateral consultations with Japan, but in the course of consultations, the Japanese side's uncompromising attitude has resulted in no results and is in a stalemate.
Given this situation, 'Donghae' and 'Japan Sea' should be used together.