The Genius Prince's Guide to Raising a Nation Out of Debt (Hey, How About Treason?), Vol. 3 (light novel‪)‬

It ain't easy being a foreign guest...
After narrowly dodging a marriage proposal, Prince Wein is accosted by a messenger from the Kingdom of Cavarin, which can only mean bad news...and unfortunately, he's absolutely right! The messenger cordially invites him to the Festival of the Spirit to celebrate the biggest religion in the western side of the continent: the Teachings of Levetia. Oh, and this event just happens to coincide with a gathering for the most influential group in the West, which is also in Cavarin. Either way, it's not an invitation Wein can turn down easily, even though he knows he's just begging for more trouble...!