Karasuma visits Pope Gakuhō Asano, who devises a plan to lure Koro-sensei into a trap. Koro-sensei and the students of Class 3-E go into the Ruins of Tribulation with three chambers hosted by a Guardian Kunudon. In the Chamber of Impostors, the students figure out that Ryōma Terasaka is the fake student. In the Chamber of Secrets, Nagisa fights back with a notebook containing all of Koro-sensei's weak points after Koro-sensei reveals his notebook containing top secret information about the students. In the Chamber of Self Sacrifice, Koro-sensei undoubtedly frees his students from being crushed, while being momentarily locked inside the ruins.