S1·E42 Old Wounds Revisited

Last year's 2nd year and 4th group teacher "Noboru Saito" stabbed his chest and was hospitalized. Saito is the person who created the cause of the current 3rd grade and 4th class teacher bullying. 　At the same time as the incident, Ya stopped coming to school. Kikuchi and Murai are suspicious that "Maybe Masa stabbed Saito?"