An arm of the western Pacific Ocean, east of the Korean peninsula, west of Karafuto (what the Russians call Sakhalin) and Honshu, Japan, north of East China Sea, south of the Sea of Okhotsk. Korea calls it "East Sea". China, Japan, and Russia calls it "Sea of Japan". Further adding to the confusion, China refers to East China Sea as "East Sea".

I didn't know Korea was requesting other countries to call the sea as "East Sea," or what they call the "correct" name. However, the problem with Korea's victim-of-imperialism argument (see below w/u) is that the name "Sea of Japan" became de facto in the first half of the 19th century, prior to Japanese expansionism in the first half of the 20th century. The name "East Sea" is just that, a name. I see no reason why other countries should change what they call the sea.

Argument for "Japan Sea" :

Argument for "East Sea" :