With three hours remaining until the laser cannon is charged, Nagisa and the others begin their infiltration of the mountain. Using their home turf to their advantage, the students knock out all the police troops guarding the area and reach Koro Sensei, who praises their efforts for coming so far despite the odds. Just as the students bring out a cake to celebrate Koro-sensei's birthday, Yanagisawa appears on the scene with the second Reaper, who has been powered up with tentacles, before injecting himself with the tentacle formula and launching a double team attack on Koro-sensei.