Mariko

A mysterious nurse who takes the students to the basement infirmary so they can take part in a special class on Thursdays. She knows all the new and old students' names and their "issues", like Ichijo's gender. The nurse also takes part in the memory loss when a student "graduates". In volume 1 Mashiro checks at the regular high school infirmary; all the staff is present and accounted for and this nurse is not one of them. The entrance to the basement infirmary is not findable except to class members, on Thursdays.…