[@Genkai]
Pretty straight forward actually....
We can just say, my character is spearheading a merchant's rebellion across hoshido and nohr, which would be in parallel to our missions. Most royals and nobles loyal to their respective crowned monarchs would despise us. The more shrewd ones would openly hate us, but secretly fund us. Perceptive nobles and merchants follow the cash flow. And if that starts to shift away from the current ruler, they will hedge their bets.
They don't even have to know about the mission to save the world. It could just be their own self-interest. =P

War is good business for some, but not for this merchant and his friends, whom are slowly withering under excessive war taxes. A few nobles who lost much of their levies during the ongoing war might join the cause as well.