First, Japanese sea is a error.In the first half of the 20th century, Japan robbed Korea of its national sovereignty. Korea was deprived of the opportunuity to make the name, 'East Sea', known to the world. How long has the name "East sea' used.
According to the Chronicles of the Three Kingdoms, published in 1145 AD, the name, " East Sea" was used as early as 59 BC. As confirmed by the Monument in memory of a great Korean King in the 5th century, and numerous other references that followed. It means that Korea has used the name, "East Sea" for over 2000 years.
However, Japan argues that the term, Sea of Japan was established in the 19th century.
Surprisingly, official Japanese maps produced up unitl the late 19th century.
We Korean's can't just let this happen.
So we are contactiong you for your help. `