You need to use the expression ‘East Sea’ in your map as well as the ‘Sea of Japan’.
Writing as ‘Sea Of Japan’ is common in the current international community, but in fact it’s one of the most controversial examples of distortion of history. Writing ‘East sea’ is at the center of a diplomatic dispute with Japan. Unfortunately, the correct facts are not publicized in the international community. I believe that’s why your website used this expression.
I’ll be waiting for the correction. Thanks for reading.