Maki Ikuta, nicknamed Makio, is a first-year student at Prefectural Umineko Commercial High School. Though part of the school's swim team, her swimming skills are initially underdeveloped; she receives continuous lessons primarily from Kaname Okiura, who employs a kickboard as her training tool. Her physical build is notably petite for her age—standing 1.45 meters tall and weighing 40 kilograms—resulting in frequent misidentification as a junior high student. This stature accentuates her youthful innocence and earnest demeanor in social settings. Her appearance features short black hair with a distinct ahoge (cowlick), violet eyes, and an overall small frame.

Personality-wise, Makio radiates cheerful energy, visibly sparking with excitement or flustering easily over new developments. She harbors profound admiration for fellow swim teammate Amuro Ninagawa, instantly mesmerized by Amuro’s unconventional yet graceful swimming technique during their first encounter. Makio fixates on her own physical development, particularly her breast size, voicing open envy toward teammates like Mirei Shizuoka who possess larger busts. She habitually touches Mirei’s breasts, often without consent. This preoccupation drives her to form an informal "Alliance" with Maaya Nanako, another small-breasted teammate, dedicated to increasing their bust size through shared efforts. Paradoxically, Makio frequently champions modesty within the team. Amid chaotic or risqué scenarios—such as clothing mishaps or the captain’s antics—she instinctively preserves propriety by covering exposed body parts, especially those of female teammates, with her hands.

Her character lacks significant development or expanded background beyond established traits. Swimming proficiency remains rudimentary throughout her team involvement, never progressing to competitive levels. Relationships—including her reverence for Amuro, alliance with Maaya, and modesty-conscious role—persist without major shifts, deeper personal history, or future aspirations.