Okiku Doll is a doll wearing a kimono. It once belonged to a little girl, Okiku. Once she died of a cold, her spirit possessed the doll. and now its hair grows.
The doll is now in the Mannenji temple.
First its hair was short but it grew over time and it now has long hair.
Nobody knows how the hair continues to grow but scientific researches concluded that its hair is that of a young child, maybe Okiku's.