OVA
Description
Mitsuko Yokoyama is a supporting character in Prison School and serves as the secretary of the official Aboveground Student Council. She is also the cousin of Anzu Yokoyama, a former member of the Underground Student Council. Mitsuko is a short, slim teenage girl with dark green hair tied into twin buns, with bangs swept to the left side, and emerald eyes. She typically wears the standard school uniform, often without a tie, and sometimes dresses with an open collar and without the blazer when performing manual labor for the student council. A frequent sight is her skirt inadvertently tucked into her underwear due to her clumsiness.

Mitsuko has a shy, kind, and mild-mannered temperament. She is notably the only member of the official Student Council who holds no grudge against the Underground Student Council, interacting with Mari Kurihara and the others in a normal, unhostile manner. Her defining trait is her extreme clumsiness, earning her the nickname Pythagorean clumsy girl. She unintentionally exposes herself or causes mishaps, and like Gakuto, her klutzy attempts at manual labor or sheer bad luck can trigger massive chain-reaction accidents that often result in minor injuries for those involved. Despite this, she is gentle and does not engage in harassment.

Mitsuko is motivated by her duties as student council secretary and her personal interests. She has a strong passion for the history of the Three Kingdoms and exhibits otaku behavior, spending time in the library and collecting manga issues. Her hidden hobby is creating her own yaoi manga, which she secretly draws using Gakuto and Joe as her main characters, revealing her fujoshi side. Her primary motivation in the story revolves around her developing feelings for Takehito Morokuzu, known as Gakuto, and her desire to connect with him.

In the story, Mitsuko meets Gakuto in the school library, and they bond over their shared experiences of embarrassing public situations. She develops a romantic crush on him, and her interactions with him form a key subplot. Her role within the Aboveground Student Council contrasts with the more aggressive members, as she does not participate in the conflict between the councils. She also becomes a source of support for Gakuto, often helping him in his endeavors.

Key relationships include her cousin Anzu Yokoyama, with whom she shares a family connection. Her most significant relationship is with Gakuto, whom she grows close to through their mutual interests and parallel struggles with embarrassment. She also maintains cordial relations with the Underground Student Council, particularly Mari Kurihara, treating them with respect. Later, her friendship with Joe becomes important as she uses him as a character in her manga, initially mistaking him and Gakuto for a romantic couple.

Mitsuko undergoes subtle development as she becomes more confident in her interactions with Gakuto and opens up about her hobbies. Her hidden talents and interests, particularly her skill in drawing yaoi doujinshi, are gradually revealed, adding depth to her character. Her growth is tied to her acceptance of her own quirks and her pursuit of a connection with Gakuto.

Notable abilities include her extreme and almost comedic clumsiness, which inadvertently creates chaos and serves as a recurring source of humor. She is also a talented artist, as seen in her ability to produce detailed yaoi manga. Her knowledge of Three Kingdoms history sets her apart and provides common ground with Gakuto, who shares the same interest.