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

 * The self destruct device implanted inside Korosensei was omitted.
 * Korosensei engages Yanagisawa and his men in a hallway instead of a library.
 * Yanagisawa's men equip heavier armor than in the manga.
 * The anti-tentacle fence took on the form of a sheet of acrylic glass instead of a gridded fence.
 * Yanagisawa's eye was damaged by a metal tube instead of a shard of the anti-tentacle fence.
 * When the final semester begins, Korosensei meets the students in the classroom rather than outside the school.

Trivia

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