There was a long-standing animosity between the two countries, Dorigan and Sutistan.
Pure historical animosity that stemmed from the nature of Dorigan's Imperial family.
Four thousand years ago, and even before that, Sutistan was the only country on the eastern continent that was a colony of Angostan, which unfortunately died before colonizing the entire world.
After the destroyer landed, Angostan's entire royalty died with its aristocratic following and extended relatives, all except one person.
The same prince that was banished and sent to Erou Island so as not to get involved in the throne's infighting.
One of the original and a key founder of the Farris Union.
Also, the one who unified the South and made hundreds of wondering tribes into one country.
The first emperor of Dorigan.
The main reason behind Sutistan's animosity. But he was also the reason Dorigan thrived as a rich, united country.