Tomonari Mashima

The homeroom teacher of Class A (Sakayanagi's class). He coordinates the teaching staff for the grade, such as explaining the special exam on the uninhabited island during the cruise. He has known Chabashira and Hoshinomiya since high school. Normally strict, he is considerate of his students and opposed the school's decision to implement the special exam "Class Vote," which forces the selection of students for expulsion.