She is a machine from Norway, created to kill Korosensei, and was registered as a student in Kunugigaoka in order to prevent Korosensei from counterattacking her. Ritsu was supposed to be sent to Class 3-E at the same time as Itona, but the latter was currently unready. Initially, Ritsu was focused only on killing Korosensei at all costs, apathetic to the interests of her fellow students who would have to clean up the messes she made with her assassination attempts. Even after Korosensei told her that gunfire was not permitted during class time, Ritsu would endlessly attempt to assassinate him regardless of the occasion. Once she was remodeled by Korosensei, she gained genuine emotion and thus, a more happy and cheerful personality. As a result, she learned the importance of teamwork and how to work with her other classmates. As such, she was willing to hide her new programming from her original creators out of gratitude.