Karin Shiraishi endures hospitalization due to pneumothorax, a collapsed lung condition curable by surgery. However, witnessing her father die during surgery inflicted severe tomophobia—a paralyzing fear of medical procedures—and recurring nightmares. Confined to the hospital, she initially defies restrictions by using her laptop to maintain a private webpage documenting her aspirations. Anonymous emails signed "Your Fan," featuring images of Hokkaido, arrive offering encouragement. Mistaking these for messages from the young physician Dr. Amakasu, Karin develops romantic feelings, straining their interactions after he offends her by calling her pampered.

Her family situation adds complexity: her brother Mitsuru, a college student, visits sporadically to support her. His eventual hospitalization for syncope, caused by overwork to ease their mother's financial burden from Karin's medical bills, forces Karin to confront the consequences of avoiding surgery. The true sender of the emails is revealed as Nurse Yuki, a high school acquaintance of Dr. Amakasu, who aimed to connect with Karin and motivate her toward the necessary operation. This revelation, combined with her brother's collapse, catalyzes significant change. Karin overcomes her tomophobia and consents to the surgery, demanding Dr. Amakasu oversee her care.

Physically, Karin uses a wheelchair. She possesses brown hair with spiky bangs, amber eyes, and a slim, pale build, typically seen in hospital pajamas or dresses adorned with ribbons. Her personality begins as timid and somewhat spoiled, but her journey demonstrates growth into resilience and responsibility.