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 Yōsuke and eventually Suzune Horikita.

She seems to be a bit of a mooch, as after spending all her points from the first month and Class D 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

Plot
In the anime's 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.

Some days later, Kei was seen having fun the pool with her classmates, getting especially close to Yōsuke. 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 (although whether they were dating at this point exactly is unknown) then proceeded to take the mid-test exams and passed with an overall score of 75.

She later took part in the school cruise, where she calls Yōsuke to hang out with her friends.

When the cruise ship heads to an island, the first year students are told they need to survive for more than a week with basic materials. Kei later got into argument with Teruhiko Yukimura about hygienic materials they would need for survival. This soon extends to Kanji Ike as well but after setting up camp, Ike apologized for his words since he went through similar as a child as she apologized for not understanding his reasons.

Much later, Kei's panties are stolen and the girls of her class have Yōsuke check the boys for it but they aren't found.

The next day, Kei is shown leading the girls as they tell the boys of the class to separate from the girls due to the underwear theft. Kei has 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 Ayanokōji, since he doesn't have a lecherous side. While Kiyotaka is picked, Kei noted on him being invisible to the rest of the class, showing that she barely acknowledges his presence in their time as classmates.

Trivia

 * She has a character issue, one of the defects that are attributed to her being in class D.