Tsubasa Arihara stands as the narrative's central heroine, distinguished by caramel-brown hair secured in a half bun with a yellow ribbon and light blue eyes. Her given name meaning "wing" aligns with her role, while her surname fuses "exist" and "field, plain." Upon enrolling at Rigahama Municipal High School, she identifies the lack of a girls' baseball club and spearheads its creation. This initiative draws together diverse teammates—beginners, lapsed players, and individuals overcoming personal hurdles—forging a unified squad.

Her background includes competitive baseball experience, highlighted by a national tournament victory in her youth. This triumph preceded a depressive episode, during which close friend Tomoe Kawakita reignited her passion for the sport. Tsubasa embodies relentless optimism and resilience, maintaining positivity through setbacks. As a leader, she prioritizes baseball's enjoyment and team cohesion over victory-driven rivalry, contrasting sharply with adversaries like Seiko High's captain. This approach unites teammates across skill and personality spectrums.

She anchors the team as a right-handed shortstop, wearing jersey number 6. Symbolically linked to sunflowers, she reflects persistent optimism and growth. Key relationships include a childhood bond with Tomoe and a competitive history with Ryo Shinonome, who initially doubts the team's potential but later acknowledges Tsubasa's impact.