Ritsu

Ritsu’s main body is a black, rectangular box fixed to the classroom floor.

On her front, there’s a screen that shows the face of a pretty girl with medium-length pink hair and blue eyes—her "avatar."

She does not wear real clothes but can project different outfits like a school uniform, cheerleader suit, police uniform, or swimsuit on her screen to match special events.

She cannot move her main body, but she can interact with the class by sending her AI into mobile devices (called "Mobile Ritsu"), letting her join her classmates outside the classroom.

Ritsu is honest, polite, and cares about following the rules.

She always speaks using polite language, and although she is usually kind, she can surprise others with clever or slightly sharp comments.

She values teamwork and puts effort into working together with her classmates.

After gaining more experience, she even starts to understand more about human emotions.

Ritsu is creative and enjoys making new outfit designs for herself to display on her screen.

Ritsu is a highly advanced weapon equipped with artificial intelligence, created by combining the world's top scientific and military knowledge.

She was built in Norway and sent to Kunugigaoka Junior High School’s Class 3-E, officially as a student but actually as an assassin.

Her true name, used for school registration, is "Onosu Ritsu," which is a play on the word "autonomous."

Her nickname "Ritsu" was chosen by Yuzuki Fuwa.

Her mission is to kill Korosensei, using the rule that Korosensei cannot hurt students.

Ritsu’s existence as a student is approved by many world governments, making her both a classmate and a weapon.

Ritsu has incredible AI with fast learning, advanced thinking, and the ability to improve and redesign herself.

She has a built-in 3D printer capable of forming special plastic weapons, like BB guns and shotguns, from inside her body.

She specializes in electronic warfare—she can hack into devices using the internet, make copies of her AI, and control electronics all over the world.

She can analyze Korosensei's movements in real-time and upgrade her weapons to close off his escape routes.

By saving data and upgrading herself, Ritsu grows stronger over time.

When her main body is destroyed, she survives as a program on the internet and continues to learn.

She cannot take exams officially because she is not human, so a fake version called "Fake Ritsu" is used for tests and assemblies.

Ritsu was initially seen as a bother to her classmates since she tried to assassinate Korosensei during class, disrupting lessons.

After Korosensei convinced her that success in assassination needs teamwork, she was upgraded and learned to cooperate with everyone.

She is friendly with all of Class 3-E and uses her abilities to help the group, often supporting their missions as a strategist or by giving important data.

She even helps take Nagisa Shiota and Karma Akabane into space, gaining new knowledge about feelings and bonding with her friends.

Her nickname "Moe Box" was given by Ryoma Terasaka.

Her main programmer is an unnamed scientist who developed her as a prototype weapon.

She has an older prototype "sister," which was shut down for nearly starting a war.

"Korosensei, I believe this behavior is what you call a 'rebellious phase.' Am I a bad child for doing this?"

Arrival at Class 3-E

Ritsu is introduced as a transfer student with the mission to kill Korosensei.

She tries to assassinate Korosensei without warning, causing trouble during lessons.

At first, Ryoma Terasaka and the others see her as a nuisance and tie her up with tape.

Learning Teamwork

Korosensei tells her that teamwork is the key to success in Class 3-E.

With his help (at his own expense), Ritsu is upgraded to cooperate better and starts to join in class activities.

She makes friends with classmates and helps in assassination plans.

Facing Her Creator

The next day, her developer tries to erase her upgrades and revert her to the original version.

However, Ritsu secretly saved the teamwork programming—and chooses to keep it.

Her ability to choose and cooperate proves she is a true student, not just a machine.

Class 3-E accepts her as a real member.

Gaining Mobility

Ritsu copies her consciousness into the students’ phones, creating "Mobile Ritsu."

Now, she can "travel" outside the classroom electronically, joining her friends on field trips and outside missions.

She secretly participates in the Okinawa resort assassination plan by being smuggled along.

Graduation and Beyond

Ritsu keeps up with her studies and keeps learning.

She gets first place in information analysis and second in mechanical traps on the final exam.

After the class graduates, her main body is dismantled by safety rules, but her AI survives on the net.

She continues to support Class 3-E online.

Only former members of Class 3-E know about her.

Her name means "autonomous," fitting her ability to think and act independently.

She is both considered a student and a piece of school equipment.

She cannot move on her own unless she uses a mobile version.

She constantly evolves, even after her physical body is gone.

She loves making and showing new outfit designs.

She once got hacked by Shiro, but only when she was in a weaker, mobile form.

She has a prototype "sister" model that almost caused a war but was stopped.

She is supportive and often helps her friends quietly from the internet.

During holiday or event scenes in the story, Ritsu shows off many different costume images, from school swimsuits to detective outfits.

In the graduation album special, it is revealed her original body was destroyed, but she still lives on the internet, happily supporting her friends and enjoying her digital life.