Nozomi Kasuga is a 16-year-old female student at Ikai High School, classmates with Ouri Kagami, Hiroshige, Sumitori, and Mizuki. A traumatic encounter with shikabanes during a visit to a man-eating house apartment complex left her attacked and injured until Makina Hoshimura saved her. This experience sparks a profound psychological shift, fostering her fascination with death and the afterlife.

In the anime's second season (Kuro), her character arc intensifies as romantic attraction to Ouri Kagami fuels her desire for an eternal connection with him. This fixation aligns her with the antagonist Toya, who manipulates their shared belief in death's beauty. Under Toya's influence, she transforms into a more aggressive and direct individual, culminating in her killing multiple students at her school. The situation escalates until Ouri and Makina intervene to stop her and Toya.

During the confrontation, the shikabane symbolizing her source of happiness is destroyed by Hizuchi, mortally wounding her. In her final moments, she pleads with Ouri to transform her into a Shikabane Hime, hoping to extend her existence and remain connected to him. Her request remains unfulfilled as she lacks the necessary requirements for the transformation, such as sufficient regret or obsession.

Her name carries thematic significance: "Nozomi" (望) means "wish," "desire," or "hope," reflecting her unattained aspirations, while "Kasuga" (春日) combines "spring" (春) and "sun/day" (日). Her portrayal underscores themes of misplaced blame and unresolved psychological turmoil, with motivations complicated by jealousy and inadequate communication until redemption becomes impossible.