@Red225
@Gravitron
A third party infiltrated both sides and is trying to reignite the war for some reason, backstabbing both sides and framing the other.
Hiiro wasn't in a position to either care or even have enough info to attempt to resolve the situation. He followed his "contract" and made sure the Demon King and co. were out of immediate danger.
The Demon King is the greatest current advocate for peace, so she NEEDS to stay alive. Her death will practically guarantee the reignition of the war.
Hell's breaking loose back at the border, and the Demon King and co. are needed to stop an imminent war.