While researching for an assignment, I found out the publication that indicates Japan's position regarding the name of marginal sea between Korean peninsula and Japan.
According to the resolution made in UN and other international organizations, the appellation of a shared geographical feature must be written side-by-side if the countries directly involved cannot make settlement.
Therefore, the proper designation method of the area is East Sea/Sea of Japan. since there has been no consent between South Korea and Japan regarding it.
Besides, I hope this email will feed into your journal, and I would appreciate if I can get a reply once you check this.
Thank you and have a wonderful day.
Yours Sincerely
Juyeon Ko