Idle Huntress promo of SSR Thor showing a blonde anime girl lying in a thronw with her butt pointed at the camera in a boobs and butt pose and her butt looking detached from the rest of her body

More detachable butts from Idle Huntress

Apparently it is just a fact of the Idle Huntress world that the huntresses have detachable butts since is the second one we've encountered.  That, or she's just relaxing behind a cushion that's shaped like a butt and legs.

(Promo for Idle Huntress, BluStar Games)