Hana is a central figure known for her role as the secretary of the Underground Student Council. She is a young woman with a deceptively innocent appearance, characterized by her blonde bob haircut and brown eyes, though she possesses an athletic and surprisingly muscular physique for someone of her slender build. Her reputation as a skilled fighter is backed by her status as the fourth-best karate champion in the inter-high school championships.

Her personality is marked by a stark duality. On the surface, she presents herself as a kind and cheerful individual with hobbies such as brewing and drinking dandelion tea and a fondness for four-leaf clovers. However, this gentle facade quickly gives way to intense violence when she is angered, utilizing her proficient karate skills to brutally discipline those who cross her, which has earned her a fearful reputation among the male students. Despite this tough exterior, she is actually quite shy, impressionable, and surprisingly innocent, often fainting or becoming mortified when faced with embarrassing or compromising sexual situations. This innocence contrasts sharply with her aggressive tendencies, creating a complex personality.

Her primary motivations and the core of her role in the story stem from a series of humiliating incidents with a male student named Kiyoshi. Initially a loyal subordinate to the student council president, Hana is assigned to guard the imprisoned boys. Her initial grudge against Kiyoshi begins when he accidentally witnesses her urinating in a forest. This event sparks an escalating cycle of revenge attempts, where she tries to humiliate him in return, only for each attempt to backfire and deepen her obsession. This obsession gradually evolves from pure vengeance into a confused and unrequited romantic crush after a forced kiss between them. Her motivations thus shift from carrying out her duties and seeking revenge to acting on her tangled feelings of possessiveness and jealousy towards Kiyoshi.

Hana shares key relationships that define her actions. She is a loyal friend and subordinate to the student council president, Mari Kurihara, a bond that dates back to their time together in a guard corps. However, her primary and most complex relationship is with Kiyoshi. Their dynamic is a volatile mix of animosity, blackmail, and a burgeoning, awkward affection, making her his primary tormentor and a reluctant love interest. She also has a noted fear of mushrooms, which stems from a past memory of a hospital visit.

Throughout the narrative, Hana undergoes significant development. She debuts as a secondary antagonist, enforcing the council's harsh rules. Following her own imprisonment for her actions, she is released early and leaves the Underground Student Council to become an apprentice for the Aboveground Student Council. By the final story arc, she assumes the role of the main antagonist, her actions primarily driven by her personal vendetta and warped feelings for Kiyoshi rather than her official duties. Her journey is one from a dutiful, violent enforcer to a girl whose personal obsession consumes her primary motivation.

Notable abilities include her high-level karate skills, which grant her superior agility, reflexes, and explosive physical strength that belies her small stature, allowing her to easily subdue opponents. Furthermore, she is not above using psychological tactics and blackmail, often wielding her intimate knowledge of embarrassing events with Kiyoshi as a weapon against him.