Outside

Grunting, you pull out of the filly, nearly losing control as she sighs in disappointment, pushing her ass out towards you, begging to be filled back up. This sight proves to be too much and you immediately thrust your hips forward, instead of lodging your rod into her marehood like you had planned, you land a grazing hit, instead sliding up past her tail, the silky fibers tearing away your barriers as you loose your hot sperm on her smooth back, marking the filly as yours as she writhes in pleasure.