Sike!
Actually, Draco did not need to lie to them. He just informed them straight up that he had cleared out all monsters within a certain range in between the Cario Continent's Genshin Plains Field Zone and the Vareas Peninsula's Tershuanzed Field Zone.
He also bluntly revealed that he planned to charter a privatized sea route for intercontinental trade. Draco told them this for three reasons. Firstly, he would need the go-ahead from the two councils - or at least, agree to pay taxes on the route - or things would become difficult.
Secondly, as Vita Kingdom's King, he was now a registered member of the Cario Continental Council. If anything, he couldn't just lie to them open-facedly if he wanted peace here in his homeland, and Vareas would likely find out anyway if he fessed up to Cario.
