Episode Title:Secret Identity Time.Episode Description:Koro-sensei, Nagisa, and Kaede help to tidy up the storage shed, reminiscing over the past year together. Just then, Kaede suddenly attacks Koro-sensei with tentacles of her own, revealing her true identity to be Akari Yukimura, the younger sister of the previous teacher of Class 3-E, Aguri Yukimura. Believing Koro-sensei to be responsible for her sister's death, Kaede stole some tentacle serum from her sister's lab and arranged to join Class 3-E in order to exact her revenge, withstanding the pain of the tentacles while waiting for the right moment to strike. Kaede later puts her own life at risk to battle against Koro-sensei in a field of zebra grass, this time with the full strength of her flaming tentacles. Koro-sensei hears her inner voice, wishing to be saved.