Nadeko Sengoku (千石 撫子, Sengoku Nadeko) is Tsukihi Araragi's childhood friend and an acquaintance of Tsukihi's brother Koyomi Araragi. She was a victim of a painful curse that caused an invisible snake to coil around her and manifest scars that resemble snake scales. During her attempts to cure herself of the curse, she met Koyomi once again after not seeing him for a long time. She is the narrator of Otorimonogatari, and the titular protagonist of two arcs: Nadeko Snake and Nadeko Medusa.