Yayoi Fushimi is a ghost who perished in the Yokohama bombing on May 29, 1945, alongside classmates Sayoko Arashiyama and Kaja Bergmann. Her spirit persists in the present, though her ethereal form gradually weakens. Confined to a wheelchair due to half-body paralysis stemming from unspecified psychological trauma, she hails from a wealthy family, evidenced by the mansion she haunts with Kanako Yamazaki, whose background is working-class. During the war, both were drafted to work in a small-scale aircraft factory, where Yayoi played piano during weekly power blackouts to entertain the others.

Extremely naive, shy, and sheltered, Yayoi displays an absent-minded demeanor, often forgetting simple words or names. This gentle, trusting nature makes her the polar opposite of the tough, resentful Kanako, who becomes deeply protective of her. Within the main storyline, time travel resolves Yayoi's paralysis; returning to the past and reuniting with Kanako during their initial meeting addresses the psychological roots of her condition, restoring her ability to walk.

In the series' structure, she serves as the storyteller for parody vignettes, quietly beginning her tales but often being cut off when she starts to say something nonsensical. Her skill at playing the piano is noted. During the second season, her connections expand beyond Kanako. She forms bonds with Hajime Yasaka, enabling time travel; with Sayaka, the cafe owner con artist; and unusually, with Josephine, a dog belonging to Takeshi Yamashiro. These relationships signify her gradual integration into broader group dynamics. Her wartime history and ghostly existence remain central to her interactions and development.