... running itself over the skin directly above his sister's slit. The girl's wiggling stopped, shock filling her body as the wet muscle ran itself over the bare flesh. His tongue flicked against the sensitive skin within, feeling the girl shudder in his grip. The unoccupied hand running between the girl's legs. Middle finger lacking any form of lubrication as it roughly pushing between her lips, into her heated hole.
The girl cried out, she herself not yet producing enough lubricant to take in the rough, dry digit. "Brother, stop!" She yelled, feeling her body relax a bit as her brother pulled the finger from her. However, the calmness lasted only briefly as she was pushed to the floor, pinned beneath her twin. "Comeon." He grinned, placing his cock at his sister's entrance. "This'll be fun." He pushed forward, listening as his sister cried out in heated pain.
Blood began to seep from Ruffnut as Tuffnut 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 brot...