Rascal Does Not Dream of His Student (light novel)

There's a new student at Sakuta’s cram school: the honor student Sara Himeji. She’s another person who received Adolescence Syndrome from Touko Kirishima and most curious of all, apparently doesn’t want it to be fixed. Exactly what sort of syndrome could it be? And while all this is unfolding, Sakuta has to grapple with the cryptic message saying that Mai is in danger!??