Reona Sugisaki is the class representative for Serina's class in her second year at Kashima school. She possesses striking blue hair, blue eyes, and a teenage physique with measurements of 84 cm bust and C cup. Her typical attire consists of the school uniform or a one-piece swimsuit, reflecting her active membership in the school swimming club.

Her personality is cold, harsh, and arrogant, traits which contribute to her isolation despite her outstanding appearance and brilliant mind. Reona exhibits refined, relaxed, stoic, and stubborn qualities, often creating a sharp contrast with Serina's demeanor. This fundamental opposition positions her as Serina's "natural enemy," resulting in frequent clashes between them. Internally troubled, she finds solace only during swimming, a time when she can temporarily set aside her worries.

Gardening and swimming serve as her primary activities. Her role expands when assigned to show the reserved transfer student, Yukimura Yukinojou, around the school. His quiet nature resonates with her, leading Reona to perceive him as a kindred spirit due to their shared disposition.