Onihitokuchi

Oni hitokuchi (Japanese: 鬼一口 or おにひとくち, meaning "one bite from an Oni") refers to a kind of kamikakushi (or spiriting away) where someone disappears due to being eaten by an Oni.

Myths & Legends
When people vanish without warning or without a trace, their disappearance is often blamed on evil spirits. There are a number of different words describing this phenomenon. When a person is said to have been kidnapped and taken to the other world by spirits, they are said to be a victim of kamikakushi, or spiriting away. These victims often come back to the world many years later, profoundly changed by the traumatic experience. Sometimes, however, a person never returns after going missing. In these cases, the victim is often said to have been taken–or rather eaten–by an oni. Oni hitokichi describes such a situation, where the victim was gobbled up in a single bite, never to be seen again.

Lovers in the Storm
A famous example of oni hitokuchi appears in the Heian Period story collection  Ise monogatari. Poet and playboy Ariwara no Narihira lusted after a beautiful and high ranking noble lady named Fujiwara no Takaiko. Because of the her high social status, it was impossible for them to have a legitimate relationship. To Narihira’s dismay, their affair could only be conducted in secret. Unhappy with the situation, one night Narihira snuck into Takaiko’s room and kidnapped her. He fled into the wilds with the girl, when a terrible storm struck. They discovered a cave and sheltered there. Takaiko stayed in the far back end of the cave, and Narihira stood watch by the entrance with his bow and arrow ready. In the morning, when the storm had cleared, Narihira went to retrieve Takaiko from the cave, but she was not there. An oni who lived in it had gobbled her up, and there was not even a single piece of her left. Her screams had been drowned out by the sounds of the storm during the night.