Middle school student Mirai Onozawa is dissatisfied with her family circumstances and, in a moment of frustration, wishes to tear everything apart. Unfortunately, these destructive thoughts seem to come true in the form of a magnitude 8.0 earthquake just a few moments later. When summer vacation begins, Mirai reluctantly takes her younger brother Yuuki to Odaiba, where a robot exhibition that he wanted to go to is being held. However, while they are in the exhibition center, the fury of a major earthquake shakes the Kanto region; helpless, both kids witness the devastating power of this natural disaster as it brings the city to its knees. In its aftermath, they stumble upon Mari Kusakabe, a motorcyclist and single mother who decides to help the young siblings. Aiming to return to their homes and reunite with their families, the group sets off on a long and hard journey through the decimated city. [Written by MAL Rewrite]

This is a two part story that happened after Rose moved in to Roy's apartment. During the preparations for Appreciation Day, Solty watches people in the city going about and preparing for the celebration and is confronted with a thought: what is true happiness? While trying to understand happiness and the complexity of human emotions, a young girl who has had a falling out with her mother confronts Solty and Rose asking for their help. "Love Shared" is actually the second half of "Opportunities Missed", while "Opportunities Missed" shows the entire story.

The students return as school is back in session for the second semester. Following their exploits on the island during summer vacation, Class 3-E continues to sharpen their blades with their sights set on their teacher, the slippery Koro-sensei. They have more to worry about than just their teacher, however, as enemy assassins, both old and new, are out for the increased bounty on the octopus' head. Moreover, their rivals in Class A, as well as Kunugigaoka Junior High's fearsome principal, stand to block Class E from achieving academic excellence. With all of these obstacles opposing them, the group must continue to work together in order to overcome their foes and accomplish their goal of successfully assassinating their teacher. [Written by MAL Rewrite]

When a mysterious creature chops the moon down to a permanent crescent, the students of class 3-E of Kunugigaoka Middle School find themselves confronted with an enormous task: assassinate the creature responsible for the disaster before Earth suffers a similar fate. However, the monster, dubbed Koro-sensei (the indestructible teacher), is able to fly at speeds of up to Mach 20, which he demonstrates freely, leaving any attempt to subdue him in his extraterrestrial dust. Furthermore, the misfits of 3-E soon find that the strange, tentacled beast is more than just indomitable—he is the best teacher they have ever had! Adapted from the humorous hit manga by Yuusei Matsui, Ansatsu Kyoushitsu tells the story of these junior high pupils as they polish their assassination skills and grow in order to stand strong against the oppressive school system, their own life problems, and one day, Koro-sensei. [Written by MAL Rewrite]