The Economics of Prophecy: Volume 2 by Norafukurou

Having saved the Kingdom from the danger of a monster flood, Ricardo returns to his primary occupation as a honey merchant. But after a confrontation in the Academy with a prominent merchant backed by the student council, he's forced to put up a shop at the upcoming school festival, a serious competitive event with the honor of the commoner students' families at stake.
Furthermore, with the ongoing election for the now empty seat of the guild representative of the Culinary Guild coming up, this festival could be considered a proxy war of the ongoing political war going on in the Kingdom. Faced with an overwhelming difference in financial strength and marketing power, Ricardo must make use of his modern knowledge of economics and business to close the gap so that his company can survive the aftermath.