Mizue Hamasaka

シスター・浜坂瑞枝,, Sister
Sister Mizue Hamasaka is an old woman who is the main person in charge of Miator. Her main duties include handing out punishments and reprimanding students when they do something wrong. The range of punishments can vary but they can get rather outrageous such as dusting the entire staircase in the enormous church. Source: Wikipedia