The Genius Prince's Guide to Raising a Nation Out of Debt (Hey, How About Treason?), Vol. 10 LN by Toru Toba
An invitation to a ceremony sends Falanya to the Delunio Kingdom on the west side of the continent. However, she discovers a sinister scheme that threatens the nation when she arrives. Meanwhile, Wein, left behind in the east, receives word that conflict between the imperial siblings has resumed. Things seem to be racing toward war on two fronts!