Kazusa Otonashi is a young girl whom Hijiri befriends in the Devil's Trill arc. Her father was a violinist before he died and his corneas were donated to Hijiri. Kazusa gives Hijiri her father's violin after he loses his own, unaware that it is possessed by a demon. Kazusa begins avoiding Hijiri later, but it turns out that she had seen the demon hiding in the violin. Her father, as it turns out had sold her life to the devil in exchange for becoming a famous violinist. The devil knew that, through Hijiri's cornea Kazusa's father is still alive and so he tries to kill Hijiri and take Kazusa.
Despite efforts to protect Kazusa, she ultimately dies when she pushes Hijiri away from falling debris caused by the demon's battle with Byakko and Suzaku, getting crushed by a collapsing pillar in the process. In the manga, she is a shinigami after she dies but in the anime this is never stated, causing some confusion when she is seen, alive and well, with Tsuzuki and Hisoka at the end of the arc. She makes no further appearances afterward.
She is voiced by Tomoko Kawakami in Japanese and Beth McGowan in English.