For a long time, 'East Sea' has been called 'East Sea', not only by Koreans but also by old Japanese. It has been almost 2000 years since we called 'East Sea' like that.
Also, regarding the IHO's regulation on the title of world's seas, the international standard name for this part of sea is 'East Sea'.
In conclusion, 'East Sea' was the name used for 2000 years from the old East Asian countries and that is the name IHO recommends as an international standard title.
So I hope that you change the map image into another one that has only 'East Sea' written.
I know this article was written in 2016, but as when we search for 'Sea of Japan', the image comes upfront.
For this sake, I hope you change the image into another one.
Or it would be okay for you to change the map itself. (Changing the title of the sea on the map.)