Seoul says it's the East Sea. Tokyo calls it the Sea of Japan.
Despite Seoul's argument that the name Sea of Japan was forced by Tokyo during its colonial rule of South Korea, the International Hydrographic Organization, the governing organization that names the bodies of water across the globe, has sided with Japan.
But that could change when IHO convenes a triennial general assembly in April, next year to review whether to keep or change the name of the sea between South Korea's east coast and Japan's western region.
And this goal is what the Voluntary Agency Network of Korea or VANK has adopted as its mission, to actively rally more international opinions and historical evidence that supports the name of East Sea.
VANK has already helped world-class publications, such as the National Geographic Society, adopt East Sea in their atlases.
"Unlike the past, international organizations do pay attention to civic proposals and non-governmental opinions, which are sometimes reflected in the decisions the IHO makes."
Other member countries of the IHO have become more aware of the name East Sea, too.
South Korea raised the issue of the sea's name in 1992 but drew little attention.
At the last general assembly meeting of IHO in 2017, member countries unanimously agreed that the two Koreas and Japan should discuss the most suitable name.
That led to an unofficial consultation between the two Koreas and Japan in April this year.
But VANK says there is more the government can do.
"For the last eighteen years, we have corrected the name from Sea of Japan to East Sea whenever it was possible. But despite our efforts, the South Korean government hasn't asked us to be part of the delegation at the IHO general assembly. I think we could really give a helping hand to the government."
VANK says the IHO meeting next year is a chance to place the correct name of East Sea maps worldwide, and more joint efforts should be placed between civic groups and the government to fulfill that goal.
Choi Si-young, Arirang News.