MONSTERS: Hone- Onna

From the Konjaku Gazu Zoku Hyakki by Sekien Toriyama

Hone-onna (bone woman) is a yokai in Japanese lore and as the name implies she is in a form of bones. She's a woman who has died but has an undying love that brings her back to life. She is seen as beautiful as she was alive, but some will see her as a rotting corpse. Those people are either not blinded by love or strong religious faith.

This undying love allows her to be with whoever she was in love with alive. She seemingly seems normal to them and herself unknown to both that she's a rotting body. The man would more than likely know that she is in fact dead, but is blinded by love when seeing her. 

She would visit them at night and they would have a sexual relationship. This could last up to weeks and unbeknownst to their lover, she is sucking the life force from him. He will eventually die and the two will be together in death.

If she is seen in her rotting form the person and informs the man what was happening. Her lover may be thrown off though and use magic charms on the home to keep her away. This only works if he truly wants that though. She may continue to visit at night as she is still unknown to her own condition. 

Within the collection of writings called "Otogi Bōko" (1666) by Asai Ryōi (this collection is the moral-free version of "Jiandeng Xinhua" (1378) by Qu You) the story "Botan Dōrō" or the Peony Lantern is about a Hone-onna. A man named Ogiwara Shinnojo would meet Yako, a beautiful woman, and they would have a sexual relationship every night. An elderly neighbor would witness the two, but instead of seeing Yako, they would see Shinnojo embracing a skeleton.

One story of Hone-onna is explained in the text "Konjaku Gazu Zoku Hyakki" by Toriyama Sekien (may be referenced to the previous story) in the story Otogi Bōko. Hone-onna is an aged female skeleton who would carry a chōchin lantern that was decorated with Botan flowers. She would then visit the home of a man she loved when alive and have a sexual relationship with him.

In "Tōhoku Kaidan no Tabi" by Norio Yamada there is an odd tale of Hone-onna in the Aomori Prefecture. It's said that an ugly woman in the Ansei period became a good-looking skeleton after death. She is said to walk around town as a skeleton to show off, likes fish bones, and would collapse upon encountering a high priest.

SOURCES:

Wikipedia

Yokai 

Myths and Folklore Wiki

Yokai Wiki