With the 21st century just ahead, the world closed the age of discord and antagonism and is opening

According to the historical record, East Sea has appeared in Korean maps since B.C. 37. East Sea has been used for East Sea eight times through “Samguk- sagi” and “Samguksa-Jeolyo”. They are B.C. 37, 256, 416, 639, and July and September 699 of the lunar calender. Since then, even China has mainly called the sea East Sea and Japan has named it the North Sea.
East Sea has appeared in the ancient records earlier than in the ancient maps. According to “Samguksagi”, King Munmu 30th drew his will that his funeral should be hold at the big stone at the entrance of East Sea. “Samguksagi” also has the record that in the period of King Hyoso, the fighting sound was heard from East Sea.
“Haedong Jegukgi” by Shin suk-ju is the good example mentioning indirectly East Sea between Korean peninsula and Japanese Islands. The preface of “Haedong Jegukgi” includes the followings: “Japan is the oldest and biggest among countries adjacent to East Sea. The land from the north of BlackDragon river to the south of Jeju and adjacent to Yugu”.
Shin suk-ju, the author of “Haedong Jegukgi”, shows his knowledge in the above that Japan who located at the south east of East Sea as a breakwater.
Therefore, it proves the recognition of East Sea as the mediterranean sea. However, East Sea found in “Haedong Jegukgi” is understood as the extended area of the present East Sea.
There are also the ancient maps with no designation on East Sea or Sea of Japan and with Sea of Korea or Oriental Sea. Therefore, the principle and reason of designation of East Sea-Sea of Japan should be studied for the extensive understandings on this problems. Prof. Seo Jeong-cheol approached the general principle and motivation of naming in the view of Acknowledgement Linguistics.

East Sea-Sea of Japan had not been well known to the Western till the late 18th century. Thus, cartographers did not designate the sea any name till the exact name was found.
Portugal, which explored the world for the first time among the European countries, was the first countries to encourage cartographers to create the maps based on the various informations about seas.
The peninsula supposed as Korea and islands as Japan have been found in Portuguese maps from the 16th century. In the map created in 1568, Korea is under the name of Conrai.
However, in the sixth book of Protugaliae Monumenta Cartographica(PMC), which was published for the 500 year anniversary to worship the death of Henrique, King of Ocean, the map made by Louis Teixerira in between 1579 and 1612 shows East Sea under the name of East Sea. And the map by Godhino de Eredia in between 1615 and 1622 put down East Sea under Mar Coria and the Pacific under Mar Lapen. However, the lack of the informations on the sea made the right designation impossible again till the 18th century.

2) The world divided into the Orient and the Western

The Western understood the meaning of Oriental as the counterpart of Western in the ancient maps with Oriental Ocean for East Sea. In this case, the sea was usually called Ocean.
For example, Oceanus Orientallis was used for East Sea in atlas of asia created by N. Sanson in 1650 as well as the map by P. Briet in the same year. The same designation had been used till 1679 when J.B. Travernier’s map came out.
By the same token, “Chinensis”, meaning Chinese, was used in some maps.
The reason that Ocean was used was the inaccuracy of geographical information, which resulted in the misunderstanding of East Sea as the Ocean.

3) Equity

For Equity, some cartographers, who were not sure about the name of East Sea, put down Mer de Coree on Korean side and Mer du Japon on its Japanese side. It is shown in some maps by anonymous and some maps by d’Anville, whose date of creation is unknown.
Equity applied to Delamerche’s map in 1829, which called Youngheung Gulf of Coree and Japanese side mer du Japan.
On the other hand, J. Wyld put down Gulf of Korea only in Korean side of East Sea, but nothing in Japanese side in his map created in 1827. But N. Witsen called East Sea Mer Orientale ou du Japon, avoiding being any side of two countries.
N. de Fer designated Japanese side of East sea of Mer Septentrionnale du Japan, meaning North Sea of Japan in his map drawn in 1705, explaining he referred Portuguese map. In the same sense, the map created by P. Schenki in 1700 shows Mare Iaponicum Occidenntale, meaning West Sea of Japan. These designations prove the efforts of cartographers to be equitable to both Korea and Japan.

4) Records of neighbor countries

According to Aoyama, who published The name of Sea of Japan studied through the ancient maps, Sea of Japan was not in Japanese ancient map at all. Thus, there is little possibility that Japanese ancient maps were the source of Sea of Japan in the Western ancient maps.
It was the late 16th century and the 17th century when Sea of Japan was designated East Sea by missionaries in the map of the Far East used for their mission instead of writing nothing.
As in Samguksagi and Goryeo-Sa(1454), East Sea was used since the era of three states. But “Sinjeong Donggukyeojiseungnam” published in 1530 is the first records with East Sea.
East Sea is the name based on the direction such as East Sea for the sea located in the west and the South Sea for that in the south. Even though the West Sea changed into Balhae, then into Hwanghae, East Sea remained as same. But it is after 1712 under King Suk-Jong’s reign that East Sea became common in the records or the maps.
China is the only one that has the objective informations about East Sea among Far East three countries. According to An Ho-sang’s presentation, East Sea has been used for East Sea since 912-1126 and Great Oriental Sea for the Pacific, which matches Ocean Oriental in ancient Western maps accidentally.
Once East Sea was called Whale Sea with Chinese characters, Whale, meaning dolphins. But East Sea appeared in the period of Chung Dynasty again. Since China considered itself as the center of the world, Yellow Sea was a kind of domestic sea, the Pacific, which was far east, was Great Oriental Sea, and East Sea was just East Sea or Little East Sea to the Chinese. Therefore, it was rooted in Chinese perception about the directions.
It was N. De Fer who used Mer Orientale for East Sea based on Chinese records. He created two Oriental maps in 1705, in one of which East Sea is called the North Sea of Japan according to Portuguese informations as mentioned earlier. The other map shows Mer Orientale with the footnote saying that Tartar called the sea, unknown to the Europeans, East Sea. This kind of a footnote in the map is quite unusual.

In Aoyama’s oral presentation, which was mentioned earlier, he answered that the ancient Western maps had included a lot of number of Korean names till the end of the 18th century. This is the truth confirmed in the ancient maps without questions. Also Sea of Japan in small number of ancient maps including Matteo Ricci’s was not common.
However, the change from East Sea to Sea of Japan after the late 18th century simply resulted from the great deal of recognition caused by increasing communication through trade, religion and studies between Japan and the Western and books on Japan. Especially, about 1,000 literatures on Japan in the 18th century augmented the perception about Japan. To the contrary, Korean banned any kind of communication with the Western then.

Why has there been so many designations related to Korea such as Mare di Corai, Mer orientale, Mer de Coree, the Western or Corea Sea and so forth in ancient maps even though there was hardly any informations about Korea?
One of reasons is the longitudinal and latitudinal position of Korea. Japanese Islands were usually drawn as the backward of “L” or the slant shape from the North East to the South West in the ancient maps of Japan including Matteo Ricci’s, not known exactly till the end of the 18th century.
To the comparison, Korea usually appeared as a peninsula located from the North to the South with the exception of being drawn as an island. This is why cartographers, who did not have any concrete informations, hesitated to put down Sea of Japan for East Sea.
So to speak, cartographers had preferred names related to Korea till the late 18th century.

It is related to the direction of the Western perception that names such as Sea of Korea, East Sea, Oriental Ocean and little Oriental Sea were used when the Westerner did not have any informations about East Sea in the 18th century.
For example, in the Oriental culture, both thinking and writing goes from the right to the left. However, in the Western culture, it is from the left to the right.
For example, the subject comes first. Then comes the verb, which is influenced by the sex and the number of the subject. Thoughts develope the same way. Thus, the sea at the right of Korean peninsula should be named with the consideration of Korean peninsula. The direction of the perception influence the designation of East Sea.
Nevertheless, the change to Sea of Japan resulted from various communication between Japan and the Western through the Netherlands and Korean policy to close to the Western, as I mentioned earlier.