"This is crazy," Mark muttered, standing up and walking over to the window. He looked down at the quad below, where students were milling around, oblivious to the chaos that was about to unfold. He snapped the heavy curtains shut. He had enough to deal with between his heavy class load and his on-campus job. Now, his sisters had to show up and tempt him in a way a brother should never be tempted.

Mary and Marissa were identical twins, both with long, wavy blonde hair and piercing blue eyes that could make any man melt. They had always had a competitive streak, but this was taking things to a whole new level. They had shown up unannounced, their luggage abandoned in the hallway outside the dorm room, wearing nothing but matching, skimpy lingerie covered by their coats. His heart raced as he tried to ignore the images that kept popping into his mind.

"Mark, please," Marissa whined, her voice laced with desperation. "You're the only one we can trust. We just want to feel what it's like with someone who won't judge us. Someone who loves us."

Her words cut through the fog of disbelief in his mind. He knew they had always had a close relationship, but this was crossing a line that seemed to have appeared out of nowhere. The room was thick with the scent of their perfume. The sight of them kneeling on his bed, begging for his touch, was more than he could handle. He felt his resolve wavering, the heat in his body building with each passing second.

"But you're my sisters," he managed to say, his voice hoarse. "This isn't right."

Mary looked up at him, a seductive smile playing on her lips. "We know, Mark," she purred, "but we're also adults. And we've had these... feelings... for a long time." She reached out and traced a finger along the waistband of her panties. “Don’t you think we’re pretty?” She batted her lashes.

Mark swallowed audibly, “that’s beside the point.” He urged the blood to stop rushing to his cock.

The fabric of the twins' lingerie was so thin, it was almost as if they were naked before him. The way their breasts heaved with each breath was hypnotizing. He could see the hardened peaks of their nipples through the sheer material, and the outline of their pussies, already wet with desire. Despite his better judgment, his cock began to swell.

Marissa took a step closer to him, her hand reaching out to touch his chest. "We just want to know what it's like," she whispered, her eyes locked onto his. "To have you inside us. To feel the warmth of your body."

Their words were like a siren's call, and his body responded despite any reservation he had. His cock grew harder and he felt his resolve slipping away. He knew this was wrong, but the allure of his sisters' bodies was too strong to resist. They had always been flirty, but this was a game-changer.

Mary took the lead, standing up and letting her coat fall to the floor, revealing her naked body. She walked over to him, her hips swaying with purpose. "We're not asking for forever, Mark," she said, her voice low and sultry. "Just one night. One night of passion and then we'll go back to being the sweet little twins you know and love." She smiled mischievously at her sister like she didn't quite mean the promise she was suggesting.

Mary’s hand found its way to his crotch, gently squeezing the growing bulge in his pants. The heat from her touch was unbearable, and he felt his cock throb in response. Marissa followed her sister's example, shedding her coat and approaching him from the other side. They both leaned in, their breath hot against his neck as they whispered sweet nothings in his ears, their breasts pressing against his chest.