Madoka Narumi is a supporting character in the story. She is the wife of Kiyotaka Narumi and the sister-in-law of Ayumu Narumi. She works as a police detective and possesses considerable investigation skills, though she is frequently outsmarted by Ayumu in cases. Her demanding job leaves her rarely at home, and she is unable to handle domestic tasks. Madoka cares deeply for Ayumu, who is her only remaining family after Kiyotaka's disappearance. However, she is somewhat selfish and does not fully recognize the emotional burden Ayumu carries in his efforts to protect her.

Her primary motivation stems from the night her husband vanished without a trace, which shattered her. She dedicates herself to using her skills and resources to track any clue that might lead to Kiyotaka, but she often reaches dead ends. When the Blade Children emerge, she attempts to investigate them for leads, but Ayumu deliberately keeps her in the dark about his involvement for her own safety, which frustrates her. She tries to prevent Ayumu from getting too deeply entangled with the Blade Children, but her own safety becomes a weakness that Ayumu must consider.

In the story, Madoka fills a supportive role, providing professional detective insight and a personal connection to the protagonist. Her relationship with Ayumu is strained by her desire to protect him and his desire to protect her in return. She appears in both the original series and the prequel Spiral Alive. Physically, she has medium-length black hair and gray eyes. Her character shows little overt development, remaining consistently dedicated to finding her husband and caring for Ayumu, though she remains unaware of the full scope of the dangers surrounding him. Notable abilities include her sharp investigative instincts and her persistence as a police detective.