Trained Step Sister pt.4

Mark came out of his room the next morning to find Allison crouched in front of his door, stark naked.
“They’ve left for work.” She informed him as a panicked look crossed his face.
“We have just enough time for a quickie.”
Mark unzipped his cargo shorts and pulled out his dick, shoving it into her mouth with no ceremony. He was still upset with her from last night, and felt pretty aggressive. As he quickly grew to his full size, she tried to back off of him a bit, but he grabbed her head and held it in place until his crown was pushing into her tonsils. She started to choke until she relaxed her throat enough to swallow him down, and Mark sighed with pleasure.
“That’s a good little slut, take my dick all the way down.” He stood still and pulled her head back and forth, forcing his balls to her chin on every stroke. He looked down at her blonde head bobbing back and forth, her nose pushing against his stomach, when he started another tirade.
“You’re nothing but a cheap whore; you should be offering 5 dollar blow jobs in alleyways.”
He pushed her head back off his cock and shoved her backwards. She landed back on her ass with a hurt look on her face. He grabbed her hair and hauled her to her feet, making her cry out, then spun her around and pushed her face against the wall and held it there. He shoved himself into her as deep as he could on his first stroke, and began rapidly thrusting in and out. Allison squealed in pain as the teeth from his zipper began mashing into her vulva.
“Shit! Mark, you’re hurting me!” She complained. He responded by increasing the force of his thrusts and smacking her ass with his free hand.
He was fed up with her bullshit, and he intended to teach her a lesson. She gnashed her teeth and wailed as the sharp teeth of his zipper tore at her tender vaginal lips. She reached back with her hands, trying to get him to slow down, but it was no use. He merely brushed them aside and slapped her ass again, hard.
“Mark, please!” She pleaded with him. “Your zipper!”
Mark looked down and could see where his zipper was hitting her. For a brief moment he felt a pang of sympathy, but it soon passed. He snarled at her and slammed in a few more times for good measure before he paused to undo the button on his shorts, and resumed his powerful thrusting as they feel to the floor by his feet. Allison sighed in relief, but quickly discovered that his body was now slamming into her right where his zipper had been mashing into her, and it stung.
With her cheek pressed against the wall, all she could do was endure it. While pain normally turned her on, this was more than she was used to, or even wanted. She put her hands flat on the wall and closed her eyes, hoping that he would be done soon. She started squeezing her pussy around his cock, hoping to milk his orgasm out of him.
Mark could feel the sensation and grinned.
“Yeah, you like it.