Jeff was excited and didn't know what to expect. He anticipated possibly becoming older and they might have sex for the first time, or maybe becoming a physical copy of Jenny's favorite boy band singer, or her favorite actor... and having sex for the first time. Maybe she would change herself into the confident woman she always wished she was and they would have sex for the first time! Maybe she wouldn't change Jeff into a specific person but maybe a type of person like an athlete, or a biker, or a cowboy, or even a werewolf, or a vampire and then they would make out and have sex for the first time...
Jeff wasn't just thinking about sex, maybe Jenny would want to turn him into a kid for the day and try being a parent, then after a wonderful day of being a mom and visiting the zoo or something, she'd turn Jeff into a man, and make Jeff turn her into a mommy for real as she calls him Daddy and... okay, maybe he has a little bit of a one track mind...
What Jeff WASNT expecting, was for his girlfriend to activate something, rush into his arms, and then melt. He definitely thought something went wrong, but his body horror hit the roof when the goo that Jenny became started crawling all over his body, turning black, and he could feel it working its way into his skin.
High pitched screams of terrified confusion were coming from somewhere, Jeff realized a second later, it was him. Anna rushed into Jeff's room at the sound, Jeff looked up pleading for help but, though she said, "Its going to be okay Jeff, just hold still." he felt no comfort seeing his little sister beginning to melt like his girlfriend just did now that she had gotten in range of the emitter and Jeff. Jeff may have panicked less if not for Anna's final garbled words being "I need to get inside you!"
Jeff couldn't go anywhere, but like a caged animal he tried to get away. He didn't realize his center of gravity was off, or that he was screaming, or that once he had crawled onto his bed that he was struck mute. A second later when he collapsed he did realize he was paralyzed and he noticed a hungry sounding voice in his head telling him to be still and that it needs its other half...
Jeff lost consciousness as the mass that used to be his sister mounted his bed, and then him, and collapsed onto his stomach spreading over his unresponsive chest and legs.
Jeff awoke a moment later to a pile of his sisters clothes lying on top of him and his girlfriend's clothes at the foot of his bed. He sat up not feeling the extra 40 lbs he'd just gained as the symbiote was augmenting his movements. Appearance wise however, his skin was saturated with black. As he noticed this a voice in his head asked, 'Jeff? Can you hear us?' came an indistinct voice.
"Hello?" Jeff couldn't place the direction of the voice nor who it was. "Who's there? Where are you?"
'We are you and we are in you.'
"Jenny? Anna?"
'Once we were, but now we are Jeff.'
Jeff felt a shiver of excitement within him, unsure if it was from him or 'us'. Jeff thought for a moment piecing some of this together. "Oh, you wanted to be a superhero, wait, you aren't slowly killing me like in in that franchise are you?"
'We do share resources but we are a symbiote, not a parasite... to you.'
"So, okay, our superhero name together could be... hmm... Devour? I don't know if you're anything like the franchise but it can do. I will call you Devour, and together we are Devour. This will be neat! What do I need to do now?"
'We are Devour. That will work. Yes, grab the emitter, there is more we must do.'
Jeff did so unaware he was now being used to help set Jenny's former father up for infection. Innocently enough Jeff went to the bathroom and had Devour figure out how to hide and not pigment his skin. Simulating clothing resulted in destroying what he was wearing before being able to simulate clothes and causing his pocket contents, mainly his phone, to fall. Jeff realized his little sister was part of Devour and was embarrassed before Devour assured him "Anna" didn't see anything or think anything of the situation, not realizing Anna was now reduced to a smattering of impulses to add some creativity to Devour's ideas.
"Oh, if Anna can't see this..." Jeff cautiously uncovered himself thinking he was talking to his girlfriend, "like what you see?" Jeff looked at himself in the mirror, feeling another shudder run throughout him. "I'm not a jock or anything but I'm decent." Jeff said a little hurt, misinterpreting the shudder as disgust. "I can bulk up, and in a year or so my beard will come in."
'Mmm, yes. Those things will make you even better.' Devour said lustily, leaving Jeff to wonder if he had misinterpreted things initially or if Jenny secretly wanted him to become a jock.
"All right, now what?" Jeff asked grabbing the emitter and planning on discussing what Jenny wants from him when Anna isn't attached to them.
'Yes, now we need Devour's mothers and older sister.'
"What do we need them for? We are going to go out and do hero stuff or something and I don't want them around to get..."
'We must complete my sibling and give it to its host!' Devour did something to Jeff, he simultaneously became erect and horny, but also felt shooting pains throughout his body.
"God Jenny, calm down! That hurts!" Jeff was for the first time, scared of his girlfriend, not that Devour has a gender beyond Jeff. "My mom and Amber went to the mall for..."
Black tendrils shot out of Jeff's 'clothing' affixing to the walls and any surface that could support them by helping to catapult their mass through the house and out the door much to Jeff's shock and alarm. Jeff was about to be rocketed through town in a similar fashion, but his Mother's car was in the driveway and the pair were going through the trunk and back seat collecting their treasures, within range of the emitter.
"Oh heya Jeff; would you mind..." That was Amber, there was a buzzing in Jeff's head, a pulsating he could almost understand, his eyes closed trying to decipher it. The thing in him was communicating... with his family members? There was a long pause before the sentence finished, "...taking us to your girlfriend's house?" it didn't sound like amber or his mother...
Jeff looked up at the sudden mental quiet, the strange request and voice, his mother and sister were physically merged into a grotesque abomination of what once were two people. "I just don't seem to have myself put together as of yet." The thing wheezed from its multiple mouths.
Jeff was pushed by Devour, and chided not to be rude. The melty abomination that was his sister and mother was dripping biomass as it hobbled to the passenger side and squeezed in. "I hate for you to see us like this but its really just such a big help." It wheezed in unison out of its multiple heads. The passenger window was rolled down and an arm was left dripping fluid out the car window as the pair continued to adjust their fusion.
It took another prod from Devour before Jeff moved toward the driver side, got in, took the keys from his mother's purse, and started the car... Jeff didn't mention putting on a seat belt given the form of the creature next to him...
"You know Jeff, you could make quite the woman." His mother's voice said, "Yes, with our help, all the boys and girls will come flocking to you." added his sisters voice.
There were fireworks of communication going off in his head but Jeff was happy to answer this one on his own, "Um, no thanks, I'm actually excited to grow into a man."
"Your loss..." the abomination cooed as three of its arms caressed itself sensuously. Jeff shuddered in disgust.
Jenny's family's house was reached and though Jeff was ready for this to end he wanted out of the car most of all. Standing in the driveway Jeff's arm shot up and a tendril shot the doorbell before recoiling back as if nothing happened. The mother/sister abomination was working hard to exit the vehicle.
Lilith opened the door, "Jeff? Jenny is out at the mall with her friends and won't be back till later. I'm actually glad you're here though, we should talk about you breaking up with my daughter. You are becoming quite the distraction for her and..." she took a step closer to Jeff getting in range of the emitter and Jeff was no longer her priority, "...My sisters are here!" She seemed to sense them as her skin became saggy and barely clung to her as she rushed out to the driveway to the abomination, the trio could finally let go of their forms and merge into a complete symbiote.
Jeff wanted to feel disgusted, he wanted to feel disturbed, but instead of seeing a grotesque writhing mass formed from 3 people he mostly cared about, he saw a birth. Jeff closed the front door and when he came back most of the biomass was gone and all that was left was the new symbiote and a pile of clothes, jewelry, and purses. (The emitter is removing the biomass once he is 19 feet away or it is detached from the symbiote, otherwise Jeff's room and the drive here would have been a trail of viscera.)
Devour's connection to Jeff was getting stronger. Jeff was beginning to understand the symbiote's feelings better and Devour was getting more control over Jeff's body.
Jeff could sense the new symbiote was scared, it had no host, and Jeff wasn't suitable since he had a symbiote already. Furthermore the radiation from the sun was very dangerous, It's nature is to use its host as a shield but it is fully exposed without one. If it takes too much damage it may not b able to merge with a host and or get rejected.
Jeff couldn't help but feel compassion for the thing and had the strangest feeling that it is his sibling. Jeff opened the car door and lifted the deadweight with ease trying to communicate that it should hide under the seats or in the footwell to avoid the sun. Jeff covered it with the discarded clothes and got back into the car knowing he needed to find his sibling a host, but not aware what Jenny had set up.