Gemma had made up her mind. This was to good an opportunity to waste. Wearing a tight fitting dressing gown with a perversely high hemline under which she hid her sexiest lingerie. She was literally shaking with anticipation. "I wonder how the transformation is spread?" Gemma thought. "I hope its sexually transmitted!" She felt her pussy moisten as a shiver went down her spine. She began to make her way over to her sister, who was still sitting on the couch in the middle of the family's living room. She took another long look at her sister's changed body, her pussy now drenched.
"Please. Sit" Amber instructed preparing to explain her long story, wondering how she could explain such a thing. Gemma made her way past Amber and in the process sprung her plan. She knocked the Remote from the coffee table onto the floor directly in front of Amber. "Oops" She said turning to collect it a smile spread across her face. She bent over and her dressing gown raised up her backside, giving her sister a front row view to her lace panties and firm white ass. "Let me just pick this up" She added for good measure. Gemma let out an audible groan "Ngh! No!" Her head flew back, her hands frantically scrambled to try to suppress her growing member.
Amber still bent over felt something hit her ass. Something long and hard. Opting not to turn around, she stood up slowly and let her dressing gown fall to the ground. She reversed slowing while undoing her bra. She felt the huge shaft rub against her ass cheeks and instinctively she began grinding on it. Finally she removed her panties. Now standing fully nude she lifted one leg over and straddled her sisters penis. She can now see it in front of her, as she is wedged between her sisters breasts and penis. She takes the tip into her mouth and beings to suck on it; using her hands to stroke up and down the shaft. Gemma could hear Amber's muffled pleas for her to stop, but after a while they began to falter and change. Soon all that could be heard were Ambers throws of pleasure "Don't stop! Don't stop! Oh god yes, please! Hyeees!" Her moans become more donkey like as she approached orgasm until finally she came with a mighty bray, "Hee Haaw!"
Gemma's mouthed was flooded with semen. struggling for a breath she removed herself from her sisters member. Semen flew all over her face and breasts. Once the torrent finally stopped she discovered that Ambers cum tasted rather nice, surprisingly nice, after licking the remainder from her lips she cleaned the rest of her body licking her arms and chest clean.
Suddenly she felt something brush against her leg. When she turned around to investigate she found that she had grown a tail. It swayed happily in the afterglow of her sexual encounter. "Woohoo! It worked! I'm transforming! Oh god this is so hot!" Gemma looked to Amber who was currently dazed from her orgasm. Deciding that she'd be fine in her current stupor Gemma ran to a full body mirror in the corner, deciding to go over her body to see what else if any thing had changed with her tail.
As she inspected her body she was overjoyed to find that not only had she grown a tail, but her ears had changed as well, now in the shape of a donkeys. She also found that her pussy was larger, darker and more swollen. She shivered as she touched it. Wondering what effects her plan had on her sister she walked back over to take a closer look, finding that her sister had indeed changed however only slightly so, her legs where more donkey like now than before, her feet practically hooves.
Just then Amber snapped out of her confusion. She eyed her sister up and down the changes evident. "What have you done?".
"I'm sorry sis, I've never told anyone but i have a huge fetish for this sort of stuff, I couldn't resist. I thought this was my only chance!". Gemma replied sorrowfully.
Amber stood silent for a moment. "We'll talk about this later!" She said. "But right now your the only one who can cure us! Quickly Transform or Dare?".
"Huh? The old curse? That's how this happened? I never thought in a million years that it would be real! If that's the case i'll take the transform!" Gemma replied gleefully.
"Very well. I will transform you into someone that has the power to reverse all transformation just by thinking about it, your mind will be unalterable by any transformation, so no matter what manor of transformed state your in you'll always be able to change back." Said Amber, sighing as finally she saw an end in sight.
"This is great!" Gemma thought. "Now I don't have to worry about the consequences." And with that though Gemma embraced Amber in a long kiss. She then turned around and got on all fours presenting her pussy to her older sister. "Please Amber! Fuck me! Make me a donkey!"