Tradition: Japanese Mythology
Alternative Names: お岩の鼠, Oiwa’s Rats, Rats of Yotsuya Kaidan
Category: Rat
The Myth
Oiwa no Nezumi refers to the supernatural rats that appear throughout Tōkaidō Yotsuya Kaidan, the famous ghost story and kabuki play written by Tsuruya Nanboku IV. Oiwa, who is traditionally said to have been born in the Year of the Rat, becomes a vengeful spirit after being poisoned and betrayed by her husband, Tamiya Iemon. Rats serve as her supernatural agents, tormenting those responsible for her suffering and helping bring about their downfall.
After Oiwa dies, a gigantic rat appears and kills a cat before disappearing in a flash of spiritual fire. Later, swarms of rats attempt to carry away Oiwa’s infant, gather around the severed head of Iemon’s second wife, Oume, and steal a protective amulet entrusted to Oume’s nurse, O-Maki. When the nurse pursues the rat that has taken the amulet into a river, she falls in and drowns. In another episode, a rat carrying Oiwa’s comb appears before Naosuke, indirectly revealing her death to her sister, Osode.
The rats continue to haunt Iemon as Oiwa’s revenge unfolds. They appear in his dreams, transform his surroundings into terrifying visions, destroy an important document by gnawing through it, and swarm over those who have wronged Oiwa. During the final confrontation, numerous rats cling to Iemon’s sword, causing him to drop it and allowing Osode’s betrothed, Sato Yomoshichi, to strike him down. Even as Iemon struggles against his fate, the rats continue to torment him alongside Oiwa’s vengeful spirit. In the play, they become recurring manifestations of her wrath, turning the ordinary rat into an instrument of supernatural retribution.
Sources
“Oiwa.” 新版TYZ 妖怪図鑑 (New TYZ Yokai Encyclopedia). https://tyz-yokai.blog.jp/archives/1077209622.html