Hana Midorikawa is the secretary of the Underground Student Council at the notorious prison-like school. Physically, she is a slightly short young woman with a lithe and athletic build, possessing a deceptive strength that belies her frame. She has blonde hair styled in a neat bob with square bangs that cover her eyebrows, and her eyes are brown. Unlike many of her peers, she wears blue leggings or shorts underneath her standard school uniform skirt, an addition that allows for greater freedom of movement.

Her background is rooted in her position as a loyal and trusted subordinate of Mari Kurihara, the president of the Underground Student Council. Beyond her council duties, she is a highly accomplished martial artist, ranking as the fourth-best karate champion in the inter-high school championships, holding a third-degree black belt. This athletic prowess is central to her role in enforcing the council’s harsh rules.

The first impression Hana gives is often that of a kind and cheerful individual. She has hobbies that seem gentle and domestic, such as brewing and drinking dandelion tea, and she also has an affection for four-leaf clovers. This soft exterior, however, masks a drastically different inner nature. When angered or provoked, Hana becomes extremely violent, expressing her fury with powerful and proficient karate attacks. Like many female students at the school, she initially displays considerable hostility towards the male students.

Despite her capacity for violence, Hana possesses a deep-seated shyness and innocence, which creates a stark contrast with her tough persona. She is more reserved than her colleague Meiko Shiraki, and she becomes mortified or even faints when placed in compromising or overtly sexual situations. This vulnerability is a key part of her character, as she is deeply impressionable and often finds herself overwhelmed by the embarrassing incidents that follow her.

Hana's primary motivation and central role in the story become intertwined with the male student Kiyoshi Fujino following a pivotal accidental encounter. She catches Kiyoshi watching her relieve herself in a forest after she had drunk too much tea. This event triggers a profound sense of humiliation and an obsessive drive for revenge. Her goal becomes to balance the scales by forcing Kiyoshi to urinate in front of her. These attempts backfire spectacularly, leading to a series of increasingly awkward and intimate situations between them, including her being urinated on and the two hiding together partially undressed in the school infirmary.

As a member of the Underground Student Council, Hana initially acts as a secondary antagonist, brutally disciplining the imprisoned boys. However, as her personal vendetta against Kiyoshi deepens, her role becomes more complex. Her quest for revenge culminates in her forcefully taking Kiyoshi’s first kiss, an act she intends as the ultimate payback. To her horror, Kiyoshi responds by kissing her back passionately, a moment that fundamentally shifts her feelings. When she later realizes this act was part of Kiyoshi’s plan to expose the council, her fury is absolute, but the seed of a romantic obsession has been planted.

This begins her development from a purely vengeful antagonist to a character struggling with genuine, albeit confused, romantic feelings for Kiyoshi. She swings violently between wanting to harm him and finding herself drawn to him, leading to her blackmailing him into taking romantic photographs together. Later, during the school’s cavalry battle, she and Kiyoshi are forced into hiding together again, where they end up exchanging their underwear by accident, a situation that further deepens their bizarre connection. By the final arc, her jealousy and possessiveness have grown to the point where she directly sabotages his relationship with another girl, solidifying her transformation from a side antagonist to the story’s final primary obstacle.

Her key relationships are defined by her loyalty to Mari Kurihara, whom she serves faithfully as a friend and subordinate, developing a protective instinct after seeing Mari’s vulnerable side. However, her most significant relationship is her volatile, single-minded, and increasingly complex dynamic with Kiyoshi Fujino. What begins as a mission of revenge becomes a confusing obsession and ultimately an unrequited love that drives much of the latter half of the narrative.

Among her notable abilities, her karate skills are paramount. She uses powerful melee attacks to enforce order and subdue students many times her size. Her athleticism grants her enhanced agility, reflexes, and explosive strength that can catch opponents off guard. In addition to her physical skills, she is also capable of employing psychological tactics and intimidation, using her intense focus and unpredictable nature to keep others on edge.