Timeline: before 2nd year
All of Class D students, Katsuragi, Sakayanagi, Kamuro Hashimoto, Kito from Class A, Ichinose, Kanzaki, Shiranami, Amikura, Shibata from Class B, Ryueen, Ishizaki, Yamada, Ibuki and Shiina from Class C got transported to a theater-like room summoned by an unknown person or being to which they're forced to watch a certain someone's past.