Akemi Soryuin is a second-year student in the honors class 2-A at Koyo Girl's Academy, coming from an extraordinarily wealthy family. She resides in a large Western-style mansion featuring both indoor and outdoor fountains. Her much older sister, Shion Soryuin, approximately twenty years her senior, serves as the academy's chairman and is a businesswoman. Akemi holds the position of student council president, a role she secured in her first year, and has been crowned Miss Koyo Girl's Academy for two consecutive years. Outside school, she works part-time as an office lady at PWC, a job she has maintained since age 15.

Physically tall and slender with fair skin, light blue eyes, and very long black hair reaching past her hips, Akemi typically wears a light blue tank top, dark blue compression shorts, and pink sneakers for gym attire. Despite her delicate appearance, she possesses exceptional physical strength and athletic conditioning that surpasses dedicated athletes. She can perform feats like 20 inverted push-ups, lift large boulders effortlessly, scale rock walls rapidly, and display reflexes fast enough to outpace the track team in a relay race—earning her the nickname "Koyo's Joyner." She excels in numerous sports due to natural talent and background.

Akemi presents herself as a charismatic model student, effortlessly excelling in academics, sports, and social conduct, creating a "perfect" image for her peers. However, she harbors an intense muscle fetish shared by all women in her family. This manifests openly when encountering muscular individuals, often expressed through heavy breathing or vocal enthusiasm during workouts. Her fascination began in middle school after witnessing a bodybuilding competition, though she cites joining Silverman Gym to pursue a "healthy life." She remains unaware that her affluent lifestyle and capabilities are exceptional, considering them normal.

Her relationships include supporting Sakura Hibiki's fitness journey and maintaining a friendly sports rivalry with Uehara Ayaka. She views trainer Naruzo Machio primarily as an object of muscle appreciation without romantic interest. Akemi also interacts with figures like Utsunomiya Koharu, whose abs she admires, and Reioji Ai, an athletic rival determined to surpass her after previous defeats. She has a distant relationship with her frequently traveling parents, leaving Shion to oversee her. Akemi utilized her sister's connections to join Silverman Gym upon its opening.

Additional details include her fluency in English and her family's resources, exemplified when Shion provided a private jet for her and friends to travel to America upon request. Her name combines "play" (奏流) and "hospital" (院) for Soryuin, while Akemi means "vermilion red" (朱) and "beautiful" (美).