First, international rules support the fact that using 'East Sea' to describe the body of water between South Korea and Japan. The East Sea is shared by four countries, including South Korea, Russia, North Korea, and Japan. According to international rules, names of the land or sea adjacent to two or more countries should be determined through consultation between the countries concerned. If not, it is reasonable to write side-by-side the names that those countries use. These general principals are also mentioned by international hydrographic organization(IHO) and by U.N. conference of standardization of geographical names(UNCSGN).
Next, the term 'East Sea' has been used for more time than 'Sea of Japan', 'Mer du Japon', etc. In South Korea, 'East Sea' has been used for more than 2000 years, and numerous historical records including Eight State Map(ø¢Ô³õÅÓñ), Samguksagi(ß²ÏÐÞÈÑÀ), King Dongmyeong's episode support this fact. We can also check this fact through many historical maps, including those from Japan. In contrast, the term 'Sea of Japan' or 'Mer du Japon' was first used in great universal geographic map(ÍÞæ¨Ø¿ÏÐîïÓñ) by Matteo Ricci in 1602.