There’s an aspect of Japanese folklore called “Shirikodama” or (roughly) “small anus ball”, which states that humans have a small ball/organ/jewel in or near the anus where their soul is stored.

This is what inspired the name of “The Dung Eater” in Elden Ring, who would kill people and then “defile their corpse” to ensure their entire bloodline becomes cursed, as well as the Headless from Sekiro, which has a grapple attack where it removes Wolf’s soul via the nearby orifice.