Korea Maritime Institute Website map inspection by me.

I checked map collection digital archives on KORDI,Korean Maritime Institute (国土海洋部韓国海洋研究院国立水産科学院国立海洋調査院)"East Sea Study devision Website.
http://www.dokdo.re.kr/?p_name=reference&sub_page=directory&sort=100200060001&gotopage=6

In the website, there are very few map stockd by them from 1600-1850's, so I cannot judge the analysis conclusion from 1551-1850, altough I can judge a answer from 1850-1900 only which have almost twenty maps.

1551-1600 nil
1601-1650 nil
1651-1700 nil
1701-1750 nil
1751-1800 Sea of Korea 1 (100%)
1801-1850 Sea of Korea 1 (100%)
1851-1900 Sea of Japan 20 (100%)
1901-1910 Sea of Japan 3 (100%)
Gttl 25

Checking those maps 1851-1900, they recognized those four place of name nearby Sea of Japan ;
Sea of Japan
Strait of Corea
Broughton Bay
East (China) Sea

Check map and map list, sea name in the website. Excel file (xls)