Toshi, Kenji Miyazawa's younger sister, belongs to a wealthy family yet battles a chronic, unspecified illness marked by severe coughing fits and demanding frequent care. Her condition prompts Kenji to travel to Tokyo during her studies to attend to her, though she experiences temporary recovery before relapsing.

Toshi shares a profound bond with Kenji, offering emotional support during his clashes with their father over family business practices and career choices. She engages deeply with Kenji's literary endeavors, reading his published poetry in *Azalea* magazine. As her health declines, she voices fears about her mortality and imminent death. Kenji soothes her by reading his original stories aloud and sharing his creative inspirations drawn from nature.

A poignant memory involves Toshi requesting fresh snow during her illness; Kenji brings it to her bedside, feeding it to her as comfort. This moment later recurs in Kenji's hallucinations after her deterioration. Toshi dies at 24, an event that deeply traumatizes Kenji and shapes his later works, including the thematic core of *Night on the Galactic Railroad*. Her death intensifies Kenji's emotional turmoil and isolation.

In Kenji's posthumous visions, Toshi appears symbolically through imagery like a train descending into the sea—a direct allusion to her absence and his grief. This metaphor transforms into visions of trains ascending skyward, mirroring Kenji's internal reckoning with loss. Toshi's death remains a pivotal catalyst for Kenji's declining mental and physical health, as well as his artistic explorations of mortality and transcendence.