... 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 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...