Hiromi Oka starts as an inexperienced tennis player at Nishi High School, joining the club out of admiration for Reika Ryūzaki—the team's star known as "Madame Butterfly" for her court grace. Despite early struggles, new coach Jin Munakata spots Hiromi's untapped potential and elevates her to the top team, bypassing seasoned players. This isolates her, triggering intense bullying and self-doubt, particularly from resentful senior Kyoko Otowa.

Her development centers on Munakata's rigorous training, hardening her physique and mental resilience. Battling anxiety and fragile confidence, she often breaks under pressure. Incremental improvements in technique and competitive drive reshape her rivalry with Reika—shifting from idolization to determined respect. Key matches prove her abilities, culminating in tournament victories over Reika that establish Hiromi among Japan's elite players.

Personal bonds deeply shape her journey. Her relationship with Munakata evolves beyond coaching into profound emotional reliance and unrequited affection. Simultaneously, she harbors feelings for teammate Takayuki Tōdō, though Munakata discourages romance to protect her focus. Her closest confidante, Maki Aikawa, provides unwavering support during emotional lows.

A crisis erupts in the OVA *Another Match*, set three years later: After winning the All Japan Tennis Tournament, Hiromi competes internationally in New York when Munakata dies of leukemia. The news devastates her, causing a near-catatonic breakdown upon returning to Japan. Grief leaves her unable to play, spiraling into isolation. Recovery begins under Katsura—Munakata's former tennis partner and a monk—who rebuilds her strength. During this period, she confronts parallels with Ranko Midorikawa, Munakata's half-sister, who copes with his death through self-destructive training.

In *Final Stage*, Hiromi returns to professional tennis at the international level. Her style merges Munakata's teachings with her own philosophy of resilience and passion. She secures major victories, including international titles, while navigating rivalries with Reika and Ranko. Her bond with Tōdō culminates in mutual acknowledgment of their feelings, resolving romantic tension. The series concludes with Hiromi as a world-class athlete, embodying Munakata's perseverance while forging her legacy.

Visual storytelling externalizes her internal struggles—color shifts and abstract backgrounds manifest doubt as oppressive match imagery. Her evolution from timid novice to confident champion underscores themes of overcoming grief, self-discovery, and mentorship's transformative power.