"Children's traditional youkai books often describe the otoroshi as dwelling on top of the gates to temples and shrines, waiting for impious and evil-intentioned people to pass below so that it may pounce upon them. This behavior seems to stem from a fictional account in Yamada Norio's 1974 book Tōhoku Kaidan no Tabi, and was likely inspired by Toriyama Sekien's depiction of the beast perched atop a torii gate with a bird in its claw." [1]
