Nanase Morimura transfers into Aota Academy as a second-year middle school student, swiftly joining the girls' volleyball team. She possesses extraordinary yet wildly inconsistent volleyball talent. Capable of single-handedly defeating multiple established players to secure her spot, her performance oscillates dramatically between beginner-level mistakes and unstoppable spikes and service aces. This inconsistency hides a critical requirement: her full abilities activate only through sexual arousal, with performance intensity directly tied to prior stimulation level. She guards this secret closely, initially preferring a coaching role over playing.

Physically, she stands 1.74 meters tall with brown hair, red eyes, AB blood type, and measurements of 85-55-84. To unlock her volleyball prowess, she relies on Coach Motoura, seeking him for the necessary stimulation. He becomes the first and initially sole confidant of her secret. Her dependence deepens during critical moments like championship matches, where her inability to perform without his intervention threatens the team. She participates in a training camp preparing for a national tournament in the second OVA.

Her presence disrupts team dynamics, sparking fierce competition among members for Motoura's attention, though her role as the pivotal "secret weapon" in competitions remains. She maintains a mysterious aura and an initially shy demeanor, contrasting sharply with her athletic dominance and voluptuous appearance.