I honestly don't see how this girl will have kneecaps in the next few chapters.
I mean to say; I know why she'll keep them, for the sake of the drama, but with 3 of the strongest little girls in the whole prefecture I honestly don't see this girl not missing those kneecaps.
There's gonna be some stupid crux, like the girl is from some rich family who controls the area so she gets away with practically anything. And going against her will get you removed. So that's likely an arc, her trying to have the heroine expelled so she can have the protagonist.
Still... those kneecaps look mighty crushable...