In your website, he sea between Korea and Japan is written 'Sea of Japan'.
I think it should be corrected by writing the two names - 'Sea of Japan' and 'The East sea'.
In Korea's viewpoint, the sea is positioned in the east, so we call it 'The East Sea'.
However, we can't only call it 'The East Sea' because in Japan's viewpoint, it is positioned in the west.
So, the sea should be called in both two names, not only one between 'The East Sea' and 'Sea of Japan'.
Only he problem of naming it 'Sea of Japan' is it is easy to make problems when people make the norm including particular country's name.
Also, the name 'The East Sea' is called worldwide because the sea is positioned in the east side of the continent, not only Korea but also many other countries such as China.