From the comics "Khublai Khan"
"Cherished from Mandate of Heaven, the Great Mongol emperor sends this letter to the King of Japan. The sovereigns of small countries, sharing borders with each other, have for a long time been concerned to communicate with each other and become friendly. Especially since my ancestor governed at heaven's command. Innumerable counties from afar disputed our power and slighted our virtue. Goryeo rendered thanks for my ceasefire and for restoring their land and people when I ascended the throne. Our relation is feudatory like a father and son. We think you already know this. Goryeo is my eastern tributary. Japan was allied with Goryeo, and sometimes with China, since the founding of your country. However, Japan has never dispatched ambassadors since my ascending the throne. It is horrifying to think that the Kingdom is yet to know this. Hence we dispatched a mission with our letter particularly expressing our wishes. Enter into friendly relations with each other from now on. We think all countries belong to one family. How are we in the right, unless we comprehend this? Nobody would wish to resort to arms"