Wakan Sansai Zue
In the 16th volume, first half of the Miscellaneous Morsels from Youyang of the Tang dynasty, volume 462 of the Taiping Guangji of Northern Song dynasty, the "night-going leisure woman" is a nocturnal strange bird that steals peoples' babies and about it is written, "perhaps it is the changed form of what was once someone who died in childbirth" (). In Japan, they would often wear a blood-stained koshimaki, embrace children and chase after people who accompany them. They are also mentioned in the "Hyakumonogatari Hyōban" ("They are women who died upon childbirth, and became this due to attachment. In appearance, they are stained with blood below the waist, and they are said to cry out, "obareu, obareu" ()), the "Kii Zōdan Shū" ("the ubume does not give childbirth, and if only the fetus had life, such a deep delusion of the mother remains, and thus they change to this and embraces a child at night. It's said when the child cries, the ubume does too"), the "Compendium of Materia Medica", and the "Wakan Sansai Zue". The ubume's blood-soaked appearance is thought to be because in feudal society, the continuation of the family was considered important, so pregnant women who died were believed to fall into a hell with a pond of blood.