Secrets of the Silent Witch, Vol. 4.5 (novel)

The school festival may be over, but there's no time to relax as a series of mysterious happenings takes Serendia Academy by storm. As winter break approaches, food begins to disappear, a lost girl turns up at school, students start seeing ghostly balls of fire, and the second prince gets wrapped up in a suspicious spell. It's unclear how much danger they're in, but Detective Monica and her mystery-loving partner Nero are determined to get to the bottom of whatever's going on-better safe than sorry, as they say!