According to this【Divine Revelation】, the forests that we were born in fit the conditions, they had to buy the secret medicine of the elves that lived in the "Big Kuudrun Forest". The young emperor-to-be (who was 24 years old) of the "Kilika Empire" —which will be called the 'Empire', for the same reason as the 'Kingdom'— to whom the princess was betrothed to, negotiated with the elves.