Nani was the perfect victim. Not only was she completely undeserving, but she trusted Lilo and Stitch implicitly, so the betrayal would make it that much hotter. Not to mention, incest was one of the things the book talked about, and Lilo had wanted to try it ever since she witnessed the other kids on the playground doing it. She was tempted to keep Nani alive so she could continue to commit incest, but in the end she decided not to. The hotness of making her sister die screaming would be worth the loss.

At first, Lilo and Stitch arrived normally, fully cleansed and Lilo fully dressed. Nani was overjoyed that they were okay, so very happy, and that’s just the way they wanted it. The happier she was, the hotter it would be to betray that happiness. So lost in her relief, Nani didn’t even notice when Lilo slipped something into some tea before offering it to her.

It was a special poison that would make Nani helpless, unable to pull herself up off the floor, though still able to squirm, and able to feel everything. In fact, the solution would intensify her nerves, causing each stab of agony to be triple what it might feel like normally.

Not only that, they had prepared a special fate for her. In the trees near their home, they had dug a pit, in which they placed a large tub, five by five feet wide, three feet deep, and filled with burning hot oil thanks to some handy portable heating units. Above it there was a rope with a hitch on the end, ready to lower someone down into the scalding oil.

“I don’t feel so well,” Nani muttered after drinking several sips of the tea, tumbling to the ground.

She looked up at Lilo and Stitch, about to ask them for help, but what she saw stunned her. Lilo was pulling her shirt over her head, quickly following up with her skirt, dropping them down to the floor, leaving herself naked as she hadn’t bothered with underwear.

“W-what?” Nani asked, too confused to properly word a question, her eyes going even wider as she noticed the sizable schlong dangling between her sister’s legs, not to mention Stitch whipping out his.

“I owe everything to you, sis,” Lilo said as she finished undressing herself, “You’ve cared for me and protected me my whole life, and now I’m going to repay you with betrayal. “

“W-what? What’s going on?” Nani demanded as Stitch unlatched her pants and began tugging them down.

They didn’t tear her clothing; they wanted to drag out her confusion and suffering, so they undressed her very neatly. Lilo tugged Nani’s shirt over her head as the woman squirmed weakly. After having tugged it off, Lilo sat down on Nani’s face, muffling her voice for a moment, draping her large balls against her chin as she pushed her smooth slit against her mouth. Lilo moved her hands to massage at Nani’s breasts, then slowly pulled her bra off of her as well.

“We’re gonna rape you, violently, sis,” panted Lilo, “Then kill you. You’re gonna die tonight... die SCREAMING.”

Stitch enjoyed the psychological torture too. He slid his lower cock back and forth against her panties, then poked it beneath the panties so it rubbed against her pussy. He then slowly pulled the panties off, taking a moment to push his lips against her cunt, pushing his tongue deep and taking a long lap, coiling his tongue.  Under the effects of the drug, Nani moaned even as she was muffled by Lilo.

“Like that?” Lilo laughed, “Enjoy it, that’s the last pleasure you’ll ever feel.”

Lilo and Stitch rose, Lilo leading out of the house as Stitch dragged Nani behind them.

“Lilo what is going on?” Nani asked in a panic as she was dragged down steps and to the ground, then towards the trees, while also trying to get the taste of her sister’s pussy out of her mouth, “This isn’t funny! Stop it!”

Lilo rolled her eyes, “You really think I’d do this as a joke? You’re gonna die, deal with it instead of whining like the insufferable bitch that you are!”

“Lilo I... I love you.” Nani said as they arrived at the boiling pit of hot oil, eyes large at the fumes rising from it.

“I despise you,” said Lilo. She didn’t actually. She actually loved Nani dearly, but somehow that was making this all the hotter! “I can’t wait to watch you suffer, I’m gonna cum SO HARD as I watch you DIE!” She then looked at Stitch, “This stupid cunt is my sister, so I get to fuck her pussy first.”

“Time to warm Nani up for warming up,” Stitch giggled.

Stitch flopped Nani onto her back on the ground, and grasped hold of her head. Before she had time to speak again, the monster stuffed his lower cock into her mouth. She tried to close it, and even bit down, but that just made Stitch purr as he pushed deeper, swelling out her throat before he worked into a violent thrusting motion.

Lilo took a moment to savor the look of terror and betrayal in her sister’s eyes, lapping tears from her face as it was pounded, then slid behind her. She rubbed Nani’s hot behind, then pushed her tip firmly against the entrance. She took her time again, enjoying how Nani squirmed and pressed her legs together, then dove in.

Stitch's cock was a great deal thicker than she was used to, so her attempts to scream just made Nani gag more loudly. Lilo moaned, ramming her cock hard until her belly smacked against Nani’s firm rump, tip pushing into Nani’s womb as it tore through her cervix.

“Wow this is so hot,” Lilo panted, “Of all the people I’m gonna kill, killing you will always hold a special place in my heart, sis.”

Lilo yanked free, cock slick with Nani’s cunt honey, and forced it against her asshole as well. This was quite tight, and clearly Nani had never had anything there. Lilo forced it inside, causing Nani to arch her back and struggle anew, then didn’t stop pushing until she was belly deep once again. She then went back and forth, fucking her ass and then pussy back and forth, several minutes each time.

Stitch creamed a load down her throat first, her neck swelling even more as the load emptied into her stomach. Lilo crammed into her pussy once more, cumming half her load into the hot unwilling cunt before pulling out again and blasting the second half into Nani’s asshole.

It was time for the fate they had planned to be unleashed. Lilo couldn’t wait to teach her beloved sister the definition of torment. Nani was bound in a sex swing, attached to a hitch above the pit of burning oil. It held her arms behind her back, and legs spread wide until she was almost doing a split. She swung there by her arms, legs, and neck, staring down into the oil. She didn’t need to be told what was about to happen.

“Lilo please,” Nani’s panicked voice was ridiculously arousing, “You don’t want to do this! You’ll never forgive yourself! Please don’t do this!”

“Let’s lower her slowly so we can get some good screams out of her before she’d dead,” purred Lilo as she moved to the control for the hitch.

As she was lowered, Nani broke down into sobbing shrieks, shaking her head at Lilo but too terrified of what was coming to form words. She found her horror warranted as the first bit of burning oil touched her feet, then she felt the scalding oil partially encompass her legs as she was lowered into it. The smell of burning flesh filled the area as she sunk deeper, and by the time her legs were almost entirely immersed, she was screaming and thrashing about like a panicked animal.

She tried pointlessly to pull her upper body up, but wasn’t able to, as the oil touched her breasts, moving up towards her chest, then finally touching her main torso. She felt her flesh literally boiling off her body, and soon she could do nothing but slosh about as the oil moved up to her neck. There they stopped her, not wanting her to suffocate yet, lest her suffering end early.

Lilo couldn’t believe how hot it was to watch. How had she not discovered something so fun before? She stroked her throbbing erection with one hand as she lowered the hitch with the other, then locked it in placed and moved up to the edge to get a good look at the expression of twisted agony on Nani’s face.

Being his indestructible self, Stitch was able to get more personal. He plopped into the oil himself, feeling like nothing more than an intense sauna to him, and slid up behind Nani’s struggling body. He pulled her ass back against him, and penetrated both holes from behind.  Pushing in a glob of scalding oil as he did, he began to rape her violently from behind, giving her pussy and ass one more good tearing before they were inevitably boiled into soup.

Lilo didn’t want to be left out, and though she couldn’t take a dip, Nani’s head was still protruding enough for her to kneel on the edge and pull her close, plugging her beautiful screams and turning them into equally beautiful gags as she pushed down her throat, immediately beginning to thrust violently in and out. She could barely stand the heat as she pushed through Nani’s neck, but it was worth adding more suffering to her sister’s gruesome demise.

“I’m really doing it!” Lilo gasped, “I’m murdering my own sister! This is so amazing! Oh I want to do this again and again! With the ship we can just pick out any guy or girl we want, anywhere in the world, and no one can stop us from doing whatever we want to them!”

“Hundreds... thousands...” Stitch panted, “Rape them all, kill them all. Rape them all again.”

Nani’s flesh began to come off in clumps in Stitch’s claws, boiling away from her body into the oil, which seeped deeper and deeper. Long after it should have burned her nerves away, it was still keenly felt thanks to the concoction that she had drank. Stitch finally came into her, filling her with cream, which would no doubt add flavor to the Nani soup. As he jerked back, he pulled her holes open with his claws, allowing oil to pour into her gaping pussy and ass, setting her insides aflame with torment as well.

Lilo came soon after, groaning as she yanked free, creaming her load all over her sister’s face, then pulling back to hear her final screams. They were delightful. Even as the heat increased and the cum literally boiled off her face, Stitch finally pushed her head beneath the oil. Nani took a gulp of searing oil into her lungs, giving several more thrashes before she finally ceased, very much dead.

They pulled out the tattered sex swing, which had been burned away itself, and watched Nani’s corpse boil away. They’d let her boil until she was nothing but bone and slush, then be eating Nani soup for quite some time.

The two fell asleep next to the pit as Nani boiled into soup, resting in each other’s arms, dreaming of the next day’s killing spree. And the day after that. And that day after that. They had a fun life ahead of them.