Ritsu

Attendance number 27. A new type of weapon equipped with artificial intelligence sent to Class E from Norway for assassination purposes. Although not a human, it is registered as a legitimate "student." "Ritsu" is a nickname, and the registered name as a student is "Autonomous Ritsu." It has a life-sized black rectangular body made from a collection of scientific and military technologies from around the world, including the Fridtjof Nansen-class frigate depicted in the story. The monitor on the front displays the face of a beautiful girl with medium-length hair tied in long tassels on both sides, and it can freely converse with humans. It has a function to freely mold special plastic within its body, forming numerous firearms for attacks, and evolves by modifying itself based on that data. As a "fixed artillery," the main body cannot move from the classroom, but it can easily go out indirectly by downloading its terminal, "Mobile Ritsu," onto classmates' phones. Its hobby is creating clothing objects, frequently changing into outfits like winter wear, cheerleader uniforms, and school swimsuits according to events.

Initially, it was only programmed to "kill Koro-sensei," causing trouble for the entire class by attempting assassinations even during lessons, leading to being considered a nuisance and getting restrained with duct tape by Terasaka. However, Koro-sensei advised that "cooperation with other students is essential for successful assassinations in Class E," leading to various modifications at Koro-sensei's personal expense to integrate into the class. The next day, it seemed forcibly reverted to its original state by its developer, but it had backed up the "program to cooperate with students" initially installed by Koro-sensei on its own will, being recognized as a student with the same self-awareness as humans, and was welcomed again as an official member of Class E.

Throughout the year in Class E, it continued to learn and evolve, and after graduation, although the main body was dismantled, Ritsu itself continued to learn further in the online environment.

Nise Ritsu / Onaga Nise

Voiced by: Saki Fujita

A girl who acts as Ritsu's substitute.

Originally a female student at a public junior high school, she is also the daughter of Onaga Gouki, Karasuma's direct superior. She has a taciturn personality, not prying into matters and keeping secrets. She ends her sentences with "Dasu." Except for wearing a wig of Ritsu's hairstyle, her appearance, with narrow eyes, puffed cheeks, and a nose with acne, bears no resemblance to the monitor graphic of Ritsu.

During the first semester's final exams, the chairman did not allow Ritsu, being an AI, to participate, so Karasuma negotiated with him and brought her as a substitute to take the test, receiving online lessons from Ritsu. To conceal the fact that Ritsu is a machine from the school, she also appeared as Ritsu's substitute at the first semester's closing ceremony and participated in the second semester's final exams.

During the final assassination plan's activation, she intended to go for help as someone aware of Class E's circumstances but was persuaded by her father to give up.