Fuyuyasumi no Aida Dake Gyaru ni Naru Fuuki Iinchou

Public Morals must be maintained at all times, and our unseen protagonist seems to always run into trouble with the Public Morals Head at school for breaking that rule. The last thing he'd expect however, is seeing said Public Morals Head becoming a gyaru, the total opposite image of her usual self... only during winter break?