Terry's mouth dropped, eyes wide, as she saw them, through the window opposite. It was his bedroom! Bridget was moaning with pleasure as Tom's mouth sucked on her nipple, hands inside her pants, groping eagerly.
She pulled his mouth to hers. Her expression was pure pleasure. What did she think she was doing? She barely knew him! Watching, hypnotised, as Bridget's hand freed his rigid cock, Terry's eyes widened. It looked massive! Could she handle that inside her own, tight little hole?
Tom wanted Terry, because she was still a virgin, at eighteen. He was good-looking, if a bit old. Perhaps------. Her hand forced its way down to where the juices were flowing freely between her legs.
She found her clitoris, begging to be stroked. Shuddering with pleasure, she pictured Tom's tongue working away at her wet cleft. Her sister's fingers were wrapped around his solid cock. Terry gasped at the sight as it slid into her mouth, her lips stretched round its girth.
Terry was trembling, finger working so feverishly that it was hard to keep track of the lovers. Soon, Tom was kneeling, his tongue greedily licking at the love-juices streaming from her sister's eager sex.
Then her thighs parting invitingly, and Terry bit her lip, in envy, at the sight of the bulbous, purple head of his great cock pushing it's way deep inside Bridget. Her finger suddenly seemed so inadequate.
Suddenly, Terry began to shudder with orgasm. At the same time, she noticed, they were both jerking convulsively, on the bed, and her eyes closed. When she opened them, seconds later, the opposite curtains were drawn. Had she been seen?
***
Bridget was worried. After all she'd ever said to Terry about casual sex! What if she had seen them? She had to ask.
"Are you all-right, Terry?" as they sat eating, "You seem distracted.."
Terry had schemed for over an hour before her sister came home. So much for sex being a sin if you hardly knew them! That myth was blown.
"Not worth that much. Did you and Tom get on OK? You were there for quite a while."
Bridget's face was glowing, but there was no sign of remorse, as she replied, "Yes, thanks. It was a satisfying afternoon, all in all."
'I'll bet it was!', thought Terry. Sin obviously had its compensations. Maybe she should try it for herself. She began to wash up, while Bridget gratefully scurried to the bathroom.
Later that evening, they heard the door open, smiling as Tom came in, saying "Could I borrow some coffee? I've run out."
"I'll sort you some out.", said Bridget, vanishing into the kitchen Terry silently crossed the room. Kneeling in front of him, elbows resting on his thighs, she locked her eyes on his, before speaking, in a sultry tone "Tom. I need you to help put up a bookshelf in my room. I'd do anything to repay you. Will you come back later?".
He could feel the stiffening nipples, against his knees. Her mouth was begging to be kissed, but the sound of Bridget's approach broke the spell, and Terry retreated back to her seat, dark eyes smouldering.
Bridget and her parents had finally gone out for the evening, and Terry was alone in the house. She sat, impatient, in her dressing gown. When she heard the back door opening, she hurried up the stairs, quietly.
Tom was surprised to find the place empty, and called out. Terry's voice answered from upstairs.
"Could you pass a bath-towel, Tom? I've left it on the arm of the chair." Tom headed up the stairs, towel in hand, and was brought to a stop, halfway, by the sight of Terry, in lacy red panties, holding a tiny towel across her barely concealed breasts. Trying to keep it in place with one hand, she held out her other for the bath towel, her full young lips pouting sexily. With a groan, Tom bounded up the last three steps, grabbed her satin-smooth shoulders, and pressed his lips to hers, overcome by the passion in his aching crotch. She could feel his rigid cock against her thigh, and wanted him so much it hurt. He pulled his head away, knowing this was madness, but the hunger in her dark eyes matched his own. With a groan of unabated lust, he pulled her head fiercely to him once more, and they moved with only one thought.
His hands tore away the skimpy towel, and fastened on her gloriously firm young breasts. The nipples stiffened till they were as solid as his straining manhood, and Terry was on fire, her spine turning to jelly as his teeth teased engorged nipples. Her hands frantically grabbed at the throbbing heat of his manhood.
On her knees, and desperate to feel it's salty hardness between her lips, her hands cupped his sexy bum, as her mouth moved up and down. Suddenly, he pulled away. Pushing her onto her back, he ripped off the tiny pants. Gasping, she cried out "Fuck me, please! Hard! Remember I'm a virgin! Don't hurt me too much." Seconds later, she cried in ecstasy as the full length of him thrust into her, her pleasure growing by the second. Her legs had locked themselves around the back of his, and her hips rose and fell in time with his thrusting.
She could feel her own orgasm rising, as he began to grunt and jerk convulsively. All at once, he was coming, as she bounced in orgiastic frenzy. This was the most mind-blowing thing she'd ever done. How on earth could it be called sin?
They did it, much more slowly, and Terry learned that sex was much more than just the physical. As they dressed again, Tom looked worried. She understood.
"Don't fret, Tom. We both wanted it, and boy, was it good, but just a one-off. Bridget says it's wrong to start so young, and we don't want her knowing that she and I are sisters in sin, now do we?" .
