source- https://www.dlsite.com/maniax/circle/profile/=/maker_id/RG14831.html
Artist- https://www.pixiv.net/en/users/29088547/artworks

Premise- A large female teacher in a tracksuit visits Kappa-buchi, a forbidden waterfall deep in the mountains.
She has come to Kappa-buchi to retrieve a shirikodama (a mythical organ believed to be located in the anus) that one of her students had stolen, but the kappa girl, the mistress of the waterfall, is unsympathetic.

Provoked by the teacher, the two agree to settle their dispute with a sumo match.
The teacher initially gains the upper hand with her strength, but is gradually overwhelmed by the kappa girl's magic and sexual prowess...

A legendary loincloth catfight!!

27 pages, grayscale.
Includes versions with and without text.