The Story of the Kitsune and the Demon is a series made by masa. It has wrongfully been referred to as The Onibi series in the western fandom.
It is a very complicated story, but what we can say as of now is very little. Ryou, Mai's mother, kills Akari in a show at her theatre because business, but she curses Ryou and that marks her fate. Then Akari's brother, Kanishiro, kidnaps Mai and forces her to eat human meat. After that, she eats her parents (all while she's kind possessed), and she goes crazy and starts to devour more and more people.
Small things are known, such as how Akari has a sealed altar in her basement ("Open it? Open it?"), how Shikyou manipulated Mai's fate ("They were doomed to never meet") and went distraught when she found out things weren't going as planned (hence the screaming in Oni Mikage Enbu Kyou).
The finale of the series is still blurry and not known.