1602 Mateo Ricci’s World Map 坤輿万国全図

Oldest description of "Sea of Japan" in European maps by Mateo Ricci.
He produced it in Chiniese language.　There are some copy of his World Map 1602, 坤輿万國全圖. You can see Digital Archives here(Miyagi Library.　Kyoto Univ.)
In the map, the discription is as follows;

East (China) Sea describes as Great Ming Sea,大明海
Pacific ocean Japaa coast area describes Small Oriental 小東洋
Sea of Japan describes as Sea of Japan.日本海
In the map,also there are description that Korea belongings to China.

Other related Links;
Mateo Ricci's world Map and the copies.(List)
Japanese world Maps referenced from Mateo Ricci.(Muroga Collection)

cf: Some insist there are the Sea-of-Japan description on following articles or maps.(I hadnt confirmed it yet)
1.Gozalez Mendusa's "1586, Historia de las cosas más notables, ritos y costumbres del gran reyno de la China is an account of observations in China."
2.Igacio Moreira's Map of Japan who stayed in Japan 、1590-1592 (Lisbon)

Matteo Ricci, SJ (October 6, 1552 – May 11, 1610; traditional Chinese: 利瑪竇; simplified Chinese: 利玛窦; pinyin: Lì Mǎdòu; courtesy name: 西泰 Xītài) was an Italian Jesuit priest.

Matteo Ricci was born in 1552 in Macerata, then part of the Papal States. Ricci started learning theology and law in a Roman Jesuits' school. In 1577, he filed an application to be a member of a Missionary to India, and his journey began in March 1578 from Lisbon, Portugal. He arrived in Goa, a Portuguese Colony, in September 1578, and four years later he was dispatched to China.