Yukihito Sawa endured profound childhood trauma at thirteen, witnessing his father murder his mother. The shock plunged him into catatonic muteness. His recovery began only through the dedicated care and emotional support of his older cousin, Nagisa Sawa, who gradually cultivated his return to speech.

Following his mother's death, Nagisa Sawa formally adopted Yukihito. Their relationship later evolved beyond familial bonds into a romantic involvement. Yukihito remains characterized as shy and introverted, traits persisting after regaining his voice.

Physically, Yukihito possesses distinctive green hair. Within the narrative, he connects directly to the creation of the story "Winter Cicada." Nagisa Sawa, a novelist, wove Yukihito's family history into this work, drawing from memoirs documenting the recollections of Yukihito's great-grandmother, a nurse during the depicted events.