Years after they graduated, Nagisa Shiota and Karma Akabane return to the old Class 3-E classroom and look back on the year a yellow, tentacled creature called Koro-sensei taught them while challenging them to assassinate him. Their reminiscing frames a feature-length recap of the television series, threading the students' year of trying to kill their own homeroom teacher with new framing scenes. It is a compilation film rather than a new chapter in the story.