...ffnut rapidly pounded into her. Vomit seeping into the wounds deep within her. The acid within the messy substance combined with friction, and soon the skin of either of their genitals began to dissolve. Tuffnut bit his lip, pain riving itself through his own groin. He rode his sister faster, blood helping for him to slick in and out her hole. He messily came, holding himself deeply inside as he spurted cum within the girl. The girl crying out all the same, reaching her orgasm in the same moment as her brother.
Tuffnut clumsily collapsed atop Ruffnut, their sweat soaked bodies attaching. They lay upon the floor, panting as they reminisced on just what had happened a moment before.
A few months passed, and the awkwardness between the two teenagers had progressed. Hiccup and the others often questioned them, wondering why they never fought or played like they used to. They simply shrugged it off, retorting that their fellow sibling was too idiotic for their time. The other's even attempted to sit them down, and talk to them. Besides violent outbreaks and the once Ruffnut burst into tears, not much else came from their little meetings.
Ruffnut examined her body within the mirror. Large breasts now seeming a bit more minuscule against her expanding stomach. "What's wrong with you?" She hissed at it, her usually tactic of sucking it in failing.
The door flew open as Tuffnut barged in. Sure, they may have been awkward with one another, but they s...