Haruna Kasuga is a first-year student at Arisugawa Academy and a member of the DJ unit Lyrical Lily. Serving diligently on the school's disciplinary committee, she projects an earnest and responsible image. Yet her softhearted nature frequently lands her in troublesome situations, making her a prime target for pranks by peers like Miiko and Kurumi. Despite her disciplined demeanor, composure deserts her around individuals she admires, such as Miyu or Aoi; her eyes turn helpless in their presence.

She maintains a facade of indifference toward DJ activities, but harbors a genuine passion for audio equipment inherited from her father, revealing a tendency to mask personal enthusiasm while holding deep knowledge of sound technology. Standing 163 cm tall, she is Lyrical Lily's tallest member, recognizable by her maroon hair and gold-colored eyes. Nearsightedness requires corrective lenses, leading her to wear contacts outdoors and glasses at home.

Her hobbies include collecting home appliances and audio gear, and she displays notable skill at karuta. She savors caramel candy and has a younger sister. Affiliated with the tea ceremony club, Haruna regularly extends inclusive invitations to non-members for tea parties.

Familiar with manga culture, she references shoujo tropes to describe experiences like receiving head pats. She became a fan of *The Quintessential Quintuplets* after confiscating a volume from a student and later reading it herself. Peers often mistakenly address her as "chairwoman" due to her disciplinary role, a title she consistently corrects, holding no official leadership position.