Kizoku Gakuen no Fubunritsu

The aristocratic academy of the Western Kingdom runs on countless rules that no one has written down. At a ball, the daughter of a Marquis learns her engagement is over, a harsh outcome given how close the pair had appeared. Carol de la Cassata cannot work out the reason and turns to the student council secretary, who is said to give good advice. The result is a buddy mystery pairing that earnest commoner secretary with the flippant prince who leads the council.