Oriental Sea - no established concept or definiation.
Oriental Sea had been use as a are surronding Japan incruding both Sea of Japan side and Pacific ocean side when Europeans arrival to Japan. Although on some maps they wrote in the sea of Japan place, it is not established place of name.
There are three type of description of Ocean Orientale
1.The area of North east asia incruding East China sea, Sea of Japan ,south Japan coast and Kamcazka and so on.
2.The area surrounding the Islands of Japan, both Sea of japan and pacifiq ocean.
3.The area of Sea of Japan
1540.Typus Universalis Sebastian unster World
1588.Indiae Orientalis Insularumque Adiacentium Typus
Those two map above,
Oceanus Orientalis has drawn in the south or east of Japan islets.
it seems to explain just a east of China is "Ocenus Orientalis"
or
Eeastern edge of the map they describes "Ocean Oriental"
1676.Royaume du Iapon de Signe Par le Pere Ph Briet, de la Compagnie de Iesus…
Ocean Oriental had drawin on "Sea of Japan part. Ocean de laChine has drawn on South Japan islets, pacific ocean.
1687 "Noord en Oost Tartarye" by Nic Witzen
Korean claims that There are description of "Oceanus Orientalis" on Sea of japan
(but not confirmed yet by myself)
1696.Danckerts, J. Exactissima Asiae Delineatio . . ., c. 1696
http://www.voyagerantiquemaps.com/maps/15/exactissima-asiae-delineatio.html
East Asian lagre area describes "Ocean oriental"
1702（1704）L’Asie By Priviledge du Roy, J.B.Nolin. Paris (1704).
http://www.nla.gov.au/apps/cdview?pi=nla.map-t921-e
On Sea of Japan part there describes "Mer Du Japon"
Today's East China sea to South China Sea drawn as "Mer de la Chine"
and Pacific ocean and Eastern edge of the map they describes "Ocean Oriental"
Northern part of Sea of Japan drawn as "Mer peu ou point connue, des Europeens les Tartares L’appelle Orientale"
1705.De Eilanden van Japan.
Ocean Oriental has drawn around the area of Japan, both Sea of Japan and Pacific Ocean side.
South Part of Korae and around Tsushima describes as "Mer de la Chine"
1710? アジア ゾイター
共に日本沿岸の太平洋の部分にMare Japonese n Orientale が記載
18世紀前半インドおよび中国 コーフェン（コフェンス)＆モルチエ(モルティ－ル)
日本海部分にMare OrientaleとMare de Coreが記載。
1720.MAPPE-MONDE 制作Hubert Iaillot 発行P.Mortier、Amsterdam 、French version
Sea of Japan:「MER ORIENTALE OU DU JAPON」が記載
Pacifique ocean:「OCEAN ORIENTAL」が記載＞確認できず。
1720.de l’Isle, G. Mappemonde a l’usage du Roy par Guillaume de l’Isle . . ., 1720
http://www.voyagerantiquemaps.com/maps/247/mappemonde-a-l-usage-du-roy-par-guillaume-de-l-isle.html
Sea of Japan:"Mer Oriental"
1720.Mappemonde a l'usage du roy / par Guillaume Delisle, premier geographe de S.M
Paris : Chez Guillaume Delisle, premier geographe du roy, de l'Academie royale des sciences, sur le quay de l'horloge, avec privilege, 1720.
Sea of Japan:"Mer Oriental"
1725.. Goman "Eastern Ocean" という用語を使い（韓国主張・未確認）
1734. Gergraphist I.Kirilov "Atlas of Empire of Russia"
On east of Kamchazka describes "(Mare du) Orientares"
Now I cannot confirmes Korean claim which they said in Sea of Japan there descrbes as "Vostochnoe"
Sea of japan describes as "Mare Orientale Le Mievs?"
South Part of Japan ,East China sea and philippine sea there describes as "Oceanus Orientalis"
It seems to express "Eastern edge of the map"
Also, east of Kamchazka describes "Oceanus Orientares Pares"
for express "eastern edge are of the map."
1744. Homann Heirs / Haas Asia secundum legitimas Projectionis . . ., 1744
Sea of japan describes as "Mare Orientale Le Mievs?"
1745 Asia by Sanktpetersburg scientist academy
Korean claims that "Map of Asia " Asia by Sanktpetersburg scientist academy describes
Sea of japan describes as as "Koreiskoe Mope(Sea of Korea)"
and korean claims Russian map from 1745-1791 published by his prominent map describes "Sea of Korea"
(But not confirmed yet)
1749. Le Japon G.Robert de Vaugondy [Paris] 1749
East Coast of Korea describes "Mer de Coree" (It is not sea of Japan full area, just one of the part of Sea of Japan)
South coast of Japan describes "Ocean Oriental"
1750.L'Empire du Japon. Robert de Vaugondy, Gilles, 1688-1766 Robert de Vaugondy, Didier,1723-1786
1751. Robert de Vaugondy, D. L’Empire de la Chine, 1751 (1757)
http://www.voyagerantiquemaps.com/maps/41/l-empire-de-la-chine.html
East China sea sea there describes as "Oceanus Orientalis"
It seems to express "Eastern edge area of the map
1762.Rigobert Bonne: Carte de Chinoise
1776. Rigobert Bonne: L'Empire de la Chine: avc les Isles du Japon
South Part of Japan ,East China sea and philippine sea there describes as "Oceanus Orientalis"
It seems to express "Eastern edge of the map"
1779. Detail of M.Brion de la Tour. Cartographer of the King 1779
East China Sea, Tsushima, and Sea of Japan large area describes" Ocean Oriental”
1784（1792）Carte De L'Empire De La Chine Tardieu Paris 1832
1803.Edme Mentelle. Pierre-Gregoire Chanlaire Carte de l'Empire de la Chine.Paris,
East Coast of Korea "Mer de Coree”
Sea of Japan "Mer du Japon”
South Coast of Japan "Ocean Oriental or Mer Pacifique”。
1786. Charte des Russischer reich and der von lia tartarie ギュッセフェルト【German】
Sea of Japan"Orentalische Meer”
Around the coast of Japan islets are widely "Orientalische Meer”
日本海部分に が記載
読めず。
日本海部分に Orentalische Meerが記載
日本列島南岸、フィリピン海から太平洋にかけてOcean Oriental ou Mer du Sudが記載
1807.Carte de L`Empire de Russie /F. L. Guessefeld/ Homann Heirs/Netherlands
(画像未確認） 記載：Orientalische Meer ＜どこに記載？＞
1800年代? Royaume Du Japon/ Briet de la Compagnie de Jesus/France
（画像未確認】 記載：Ocean Oriental ＜どこに記載？＞
しかし、ロシア人は1844年の最後に当局が出版した地図で East Sea を "Sea of Korea" と呼んだ。
それ以降、ロシア海軍と多くの地図は、地名に言及する際に、ヨーロッパでの名前を用いるようになった。（韓国主張・未確認）
1874.J. Migeon Chine et Coree
日本海にMer du Japonが記載。
東シナ海に、Mer Orientaleが記載。
Mer du Orientaleが出る以前は、なぜか日本の東はMar de Occidentalisが多い。
日本近海はOceano de Chinoseが多い。
1657.アジア新図 フィシェル（フィッシャー）
大タルタリア、モンゴル帝国、日本および中国新図 ウィット（オランダ） 1660？
沖縄など東シナ海の海域にMar de Orientalisが記載