Can Someone Please Explain What's Going On?! Volume 6 by Tsuredurebana

Despite their marriage starting out as purely a business arrangement, Viola is starting to bend to Cercis’s wooing and is (nearly!) ready to admit to her own feelings. Unfortunately for the pair, the neighboring kingdom of Aurantia is sending their crown prince to Flür for a ceremony to commemorate the end of the war. They’re also asking for his sister, the princess, to marry into the country as a sign of peace. But she’s picked Cercis, of all people?! To make matters worse, the crown prince himself falls in love at first sight—with Viola! Despite immediate rejections, neither of the royal siblings are going to give up easily! Viola and Cercis’s relationship will be put to the test!