There's long history between Korean and Japan. The part which is written as Mer Du Japon is Korean Penisula.
For a long time, this area was well known as "Mer Du L'est", but suddenly some conservative Japanese suggested that this sea is theirs, and emphasizing this with non-reasonable back-ups.
Also, International Hydrogrphic Organization decides to use "East Sea" (Mer Du L'est)for this area.
It means "East Sea"(Mer du L'est) is the international standard name.
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