Mina Hidaka serves as a nurse at a remote mountain clinic in Miyazaki Prefecture, her short brown hair and crisp white uniform emblematic of her disciplined yet compassionate nature. Diagnosed with melanosarcoma during her second year of high school, the terminal illness leaves her with a sharply limited future.

Her story unfolds when she escorts a young clinic patient to observe a baseball practice. A stray ball struck by Hyūma Hoshi accidentally injures the child. Confronting Hyūma, Mina slaps him in anger but reluctantly accepts his help returning the child to the clinic. This encounter sparks their connection, with Hyūma gradually becoming a frequent visitor. Their bond deepens through quiet conversations and shared moments, culminating in a vulnerable beachside exchange where Hyūma confides childhood memories, dreams, and insecurities, while Mina discloses her terminal prognosis.

Her passing three episodes later is followed by a funeral in the subsequent installment, where Hyūma—devastated by grief—descends into a depressive spiral that derails his athletic career. Flashbacks and sequel references later highlight Mina’s enduring impact on his choices and growth. During her funeral, Hyūma lays a lily on her casket, swearing off romantic entanglements forever, solidifying her as his permanent emotional touchstone.

Mina’s terminal reality and brief, transformative relationship with Hyūma amplify themes of fleeting mortality and resilience. Though her physical presence spans only a few episodes, her legacy lingers through Hyūma’s ongoing battles, shaping his evolution long after her death.