Episode 38

Past Time is the thirty-eighth episode of the Assassination Classroom anime and the sixteenth episode of Season 2. It premiered in Japan on April 28, 2016.

Summary
The captive assassin and Aguri Yukimura continue to bond over their time conversing with each other. On the anniversary of their first meeting (March 13), the crescent moon came to be as a direct cause of Yanagisawa's anti-matter research. To avoid Earth meeting a similar fate in one year's time, Yanagisawa prepares to kill the assassin but the latter turns into a tentacled monster to escape the lab. However Aguri is killed by a hidden mine, and the assassin promises to carry on teaching her students for the remainder of his life. After Korosensei finishes his story, the class realise the heavy burden that is placed on them to kill their teacher.

Manga and Anime Differences

 * When Korosensei human has start mutated, he doesn't have any self-destruct device inside him while on manga he puke out self-destruct device that was installed at Korosensei human.
 * During his rampage, the room was less spacious as he engage Yanagisawa's Soldiers on the hallway while on Manga he makes rampage on library.
 * This also happens when Tentacle mine was triggered it was on the side of the room rather than hidden inside the floor.
 * The defenses and soldiers that was set up by Yanagisawa was more heavier to the armed soldiers but more lighter on the defense barricade itself compared on manga.
 * Yanagisawa already set up anti-tentacle material fences but the soldiers are less armored while on anime the soldiers was more armored while the fences was a fiber glass.
 * The damage that took Yanagisawa's eye was different from manga itself. On anime he took damage from a tube while on manga he took damage from the shards of table that destroys Anti-tentacle fences.
 * When the last term of semester begins, Koro-sensei meets them at the classroom while on Manga he met them at the front of the school itself.

Trivia

 * The opening song Bye Bye Yesterday is not featured in this episode, instead only showing the title card.