If you see the west side of japan, you will see 'Sea of Japan".

This is a wrong expression!!

Even though you wrote like 'Sea of Japan

For Hundreds of years, there had been a lot of controversy between Korea and Japan.

All of those are about territory or territorial water.

There are a lot of evidences that insists East sea is Korea's territorial water, they're keep insisting that it is their's.

Even there is some evidences from Japan, they don't accept them.

This is a very big problem for us.