Kei Karuizawa

Kei Karuizawa is among the students with excellent grades in class 1-D.

She is situated in the second row, second seat from the left, next to her "boyfriend", Yōsuke Hirata.

Background
Despite her prominent figure in class and her constantly outgoing personality on the surface, she used to have a harsh past. When she was a middle schooler, she was the central victim of multiple bully incidents. This has left her with a scar and an emotional trauma that continue to haunt her.

Appearance
Kei is a teenage girl of average height with purple eyes and long blonde hair. While so, her hair is tied in a ponytail while the rest of it extends to her back. In her school uniform, she wears a light blue dress shirt below the red school blazer with rolled-up sleeves and a short white skirt. She walks in standard school shoes with light blue calf length socks. She also wears a blue ribbon around her collar. In a more casual clothing set, she simply wraps her school blazer around her waist and rolls up her dress shirt sleeves.

Personality
Kei is an outgoing person, spending most of her time with the girls at school and Yōsuke Hirata, her "boyfriend". She is also someone who speaks for the girls in the class, acting as one of the leaders along with him and eventually Suzune Horikita.

She seems to be a bit of a mooch, as after spending all her points from the first month and D-Class not receiving any due to their actions, asked the girls of her class to lend her some money to buy the 'essentials', managing to get at least 2000 points from Kikyō Kushida.

Abilities
She was assessed as being subpar by the school. Her absences and grades were the direct reason for her being placed in D-Class. She doesn't like academics or sports, but is surprisingly able. She has immense mental strength according to Kiyotaka and Kakeru.

Plot
In the anime, during her debut, Kei Karuizawa, like the other first years, listened to the speech given by Manabu Horikita welcoming the first years to their new school. She was seen in the class talking to Satsuki Shinohara before Yōsuke Hirata asked the class to introduce themselves, agreeing with the idea.

After Sae Chabashira had walked in and introduced to the class the system in which they are supposed to live in now, Kei was surprised at the fact that they received 100,000 points to begin with. She was seen talking with Maya Satō and Chiaki Matsushita about clothes and jewellery shopping after the classes that day. At the start of the new month of May, along with the rest of D-Class, Kei was surprised why they didn't receive the monthly allotment of points, looking depressed throughout the explanation of S-Points and how D-Class failed to keep any of their points.

At some point later, Kei started dating Yōsuke as she was seen having fun the pool with her classmates, getting especially close to him. She tried asking Kikyō to lend her points along with some other girls of the class to buy herself the 'essentials', in which at least Kikyō complied with the demand. She is seen getting closer to Yōsuke then proceeded to take the mid-test exams and passed with an overall score of 75.

During the anime pool filler episode, Kei saw Suzune walk out of the apartment building, claiming how there were rumours she had died because no one had seen her over summer break. Suzune then monologued how Kei acted in class, leading on of the two girl groups with Kikyō and how dating Yōsuke Hirata greatly increased her influence, casually implying that she was dating him for this reason only (which also implied that they have being dating since before summer break if the latter statement was noticed). Kei then left, dragging Yōsuke with her after Suzune expressed her disinterested comments about hanging out with the rest of her class.

Kei, like all the other first years from every class, later took part in the school cruise, where she was seen calling Yōsuke over to hang out with her friends. When the cruise ship headed to an island, the first year students were told they need to survive for more than a week with basic materials. Kei got into an argument with Teruhiko Yukimura about the hygienic materials they would need for survival, specifically the toilet situation. That soon extended to Kanji Ike as well but after setting up camp, Kanji apologized for his words since he went through similar as a child, as she apologized for not understanding his reasons.

Towards the end of the survival test week, Kei was shown crying in the tent as her underwear was stolen and the girls of her class have Yōsuke check the suspected boys for it but they aren't recovered, with only Yōsuke and Kiyotaka knowing where they really were. The next day, Kei along with other girls told the boys to separate from them due to incident the day before. Kei had Yōsuke watch over the boys in the class, however Suzune Horikita requested another boy watch over him since he could still be a threat. Though Kei defended her "boyfriend", she agreed but wondered which boy should help as the rest seemed lecherous, but Suzune chose Kiyotaka since he doesn't have a lecherous side. While Kiyotaka was picked, Kei noted on him being invisible to the rest of the class, showing that she barely acknowledged his presence in their time as classmates. That night, as somebody started a fire at camp burning the survival test manual, Kei questioned who's the culprit among the boys which other girls approved; however, they soon started suspecting Mio because of her absence. Later, they learnt that Suzune had dropped out due to her fever and kept discussing about Mio's action whether if she's the culprit and C-Class' leader.

The next morning, Kei was seen cleaning up the camp along with other girls. At the time of class point announcement, she and the entire class was both in shock and joyful with the result of first place. Later, they returned to the cruise ship.