In other words, DPRK has an historic claim on the entire peninsula.
How fitting that an imaginary animal that was a symbol of purity and grace should be claimed as an historic antecedent by a socialist government.
Both unicorns and socialism promise perfection, appealing to the naive. Unicorns turn out to be imaginary, which is at least benign. Socialism ultimately reveals itself to be the opposite of how it is portrayed: evil, a wolf in sheep's clothing.
I think Pyongyang (Pyongyin) was an ancient capital... then again, so was Kaesong... SEOUL means “Capital City” I believe