Momotaro and her friends want to defeat bad students from oni school that harass schoolmates from theirs.
Even though Momotaro managed to defeat to Oni, she is unable to forget the experienced futanari pleasures and becomes more and more like sadistic Oni herself, rapes her friends and returns to oni academy of her own will.
(It is revealed that all the students in oni school were originally normal humans but as their hearts became distorted by demonic pleasures they became oni)

I saw someone posted first 4 chapters of this great work and thought I will last 2 chapters. This is chapter 5.

Chapter1:
https://e-hentai.org/g/1006566/fdc556611f/
Chapter2:
https://e-hentai.org/g/1006571/01753f292c/
Chapter3:
https://e-hentai.org/g/1006569/b974a69699/
Chapter4:
https://e-hentai.org/g/1006572/4b1d0ac765/
Chapter5:
https://e-hentai.org/g/2216853/fa52c85aaa/

You can buy it here:
https://www.dlsite.com/books/work/=/product_id/BJ527178.html

Wow, I haven't seen this series since so many years ago. I remember it was good futanari. Thank you for uploading!

Base +15, 止步天籁 +6

Is this a play on the saying "He who fights monsters"?

Base +8, 止步天籁 +6

SHE WHO FUCKS MONSTERS
WILL GET FUCKED BY MONSTERS AFTER BECOMING ONE HERSELF

Base +18, 止步天籁 +6, nipponica +5