East sea and Sea of Japan

Historically East sea is Korea's history, because many historical artifacts says that East sea and Dok-do is Koreans'.
Not only Korea's artifacts say so, Japanese 19th centuries world map depicts East sea as Joseon sea which is more likely to be korea's territory. How ever there is more good idea of depicting one sea with two names.

Frist idea is to write the name East sea and Sea of Japan together. Then the two ideas go together. So this idea don't need any mathematical dizzy calculations.

Second idea is to have a territory limited line to depict the national border that we can have the western part of the sea and japan can have the eastern part of the sea.But my idea likes to be more peaceful, I want that Japan and Korea share the sea and name the sea Kopan(??) sea which have both Korea and Japan.