u/No-Couple2919

This Yōkai story dates back to the Edo period.
Every night, a white butterfly would appear in a home in Mihara, Mutsu Province, inflicting physical pain on the master of the house and overall tormenting him. One night, there was a loud noise, so when he went to investigate, a white butterfly around 5 feet tall was walking around like a person. When he slashed at it with his sword, it was blown away and vanished, and from then on, the pain seemed to cease.

If you wanna know her story, its basically some SHOCKER from Kamen Rider stuff with an evil organization kidnapping someone and converting them into a monster, however she escaped and kinda just targets random people at night time.