Dave aimed his phone at his big sister and pressed the button. "Object 1 acquired," the App said. "Analysing..."
"Hey, stop that," Bella said, glowering at him.
He grinned back mischievously and put the phone away. The App was busy anyway, a slow progress bar promising a long wait as it analysed the photo, although what exactly the analysis was for he had no idea.
Supposedly the App let you modify people sexually, which Dave guessed meant that it was like a Snapchat filter or something that removed clothes and exaggerated breasts, and stuff like that. Given that the only women around were his mum and sister, Bella was the obvious test subject.
At twenty-three, she was two years older than him, and currently 'between relationships'. He himself was still a virgin, being generally hopeless around girls; and Georgia, their mum, was single too now, the divorce having gone through finally.
Dave's dad had moved in with his young, blonde secretary, and Dave was never sure whether he was more angry at his dad for abandoning his mum, or more envious over the idea of his dad fucking Lucy's sweet, blonde pussy. Dave had had quite the crush on her himself.
The consequence, however, was that he was alone with Bella and their mum this Christmas holiday, and bored to tears because of Covid and no one wanting to party. So why not give the mysterious new App a try? Giving his sister a porn-star body would be a fun diversion.
Their mum was busy in the kitchen and Bella was binge-watching some anime series on Netflix. He was only half-watching it himself, finding the need to follow subtitles a little too distracting, but amused by the frequent up-skirt views of white panties even in the middle of action scenes.
His phone chimed. The analysis was complete. "Object 1/5: Bella," the App said, with a detailed list of attributes, from height (160) and weight (55) to chest and cup size (34C) to hair colour, length and style (auburn, shoulder-length, straight). And much more too. The dimensions of her nipples ('8/8', whatever that meant), the colour and style of her pubes (auburn; natural), a description of a tattoo on the side of her breast (the name of the hated ex).
Dave was stunned. The App knew stuff about her that he himself did not, and that certainly couldn't be guessed at from a photo. And not just physical stuff either. Her relationship status (single, with a mild obsession for her ex), her orientation (straight), her libido and arousal levels (low and none), her kinks (light bondage).
*
Bella switched the television off and stared at her brother. Dave was studying his phone, his eyes wide in amazement, and yet somehow she knew he was looking at her. That in some indefinable way she belonged to him. "What are you doing?" she asked.
Dave looked up, startled to find her looking at him. "Nothing," he said, putting the phone away hurriedly. As if that wasn't sufficient evidence of guilt, his cheeks flushed bright red.
Bella laughed. She crossed the room and joined him on the sofa. "Let me see," she insisted. When he shook his head emphatically, gripping his phone tightly, she gave him her sweetest, most disarming smile, and said, "I promise not to be upset. Please let me see."
Dave hesitated still for a long minute, but then yielded a little. "You promise?"
She nodded earnestly. Whatever perversion was on his phone, she felt that it was important for her to see it.
Bella had never seen her brother look so frightened as when he handed over his phone. She took it carefully, saw her name and photo, and studied the long list of details below. "How the fuck do you know all this?" she hissed. "Are you stalking me?"
"No!" he cried in desperate denial. "It's the App! I just took your photo and the App figured out the rest somehow."
"Right," she said, her voice dripping with sarcasm. A menu option took her to an Object List with five possible entries. Currently Bella was the only object. "I'm not a fucking object," she muttered.
Tapping one of the others brought up the camera, and she snapped a photo of her brother even as he flung up his hands with a cry of, "No!"
"Object 2 acquired," the App said, making Bella chuckle. "Analysing..."
"Give it back," Dave cried, snatching at the phone.
Bella held it out of his reach. "Fair's fair," she said. "If you know everything about me, I want to know about you.
After a minute, the phone chimed. "Object 2/5: Dave," the App said.
Bella quickly scanned the detailed list of attributes, and laughed. "Only three inches? You poor thing! No wonder you're a virgin." A moment later she saw the kinks and gasped. "Mild incest? Oh my God! Is that true?"
*
Dave finally managed to grab his phone back from her, and ran away to his room, Bella's laughter echoing in his ears.
Once alone, his door shut and locked, he studied his own details. It confirmed what his sister had said, including the mild incest kink. For his penis it said '83/56', which he recognised as the length and girth in millimetres.
But Dave knew something Bella didn't. The App was supposed to be able to modify people somehow, and maybe it wasn't just a filter effect.
After a few minutes' experimentation, he found that pressing and holding on a detail brought up an editing field. Quickly he returned to his penis dimensions and added a couple of zeros.
A sudden rush of heat in his crotch had him scrambling to remove his trousers and boxers, and he stared down in astonishment at a limp cock that hung down to his knees and was nearly as thick as his legs. "Holy fuck!" he shouted.
Thinking about how much blood was needed to fill that cock for an erection, he decided abruptly that while bigger was generally better, some moderation was due. Several experiments later, he decided he was satisfied with twelve inches in length and seven in girth. He amused himself by watching it grow erect and then limp as he adjusted his arousal in the App.
The incest thing bothered him. He nearly deleted it, but then had a better idea. He switched to Bella's profile, added 'incest' and 'exhibitionism' to her kinks, deleted her lingering obsession with her ex, and changed her tattoo to read 'Dave'. On a whim he changed her orientation to 'pan' and bumped up her cup size to 'DD'; and curious about the '8/8' of her nipples, he changed them to '16/16'.
A hammering on his door nearly made him drop his phone. "Dave!" his sister screamed. "What the fuck are you doing to me?"
Laughing quietly, he increased both her libido and arousal, then hid the phone and unlocked the door.
*