It is ambiguous and Korea-centric. The Sea of Japan is not east of Japan, it's only east of Korea, while it's south of Russia. Korea loves to name seas in reference to herself (South Sea, West Sea).
lol @ the North and South Korean nationalists trying to push their propaganda in a video game comment section...
"East Sea" is too ambigious and is confused with the East China Sea and the Pacific Ocean.
It's internationally recognized as the Sea of Japan. Deal with it.