Episode 37

Confession Time is the thirty-seventh episode of the Assassination Classroom anime and the fifteenth episode of Season 2. It premiered in Japan on 22 April 2016.

Summary
The battle between Kayano and Korosensei concludes with Nagisa using Irina's kissing technique on his friend and Korosensei removing her tentacles. As promised, Korosensei begins to tell his story of how he was the original God of Death, and meeting Aguri Yukimura while in captivity by Shiro.

Anime and Manga differences

 * On the manga he was seen make some attempt to escape multiple times with multiple methods, some of it like try to brainwash some of the scientists or even ripping Yanagisawa's neck off with biting him but on anime it didn't even mentioned about the methods to attempt to escape.
 * Aguri's expression on anime was more calmer rather than on manga where she was mostly in awe or suprised because of being taught by Korosensei.
 * The previous batch on Class E was not shown on anime which skipped directly to the current generation of Class E.