After years of gruelling research, the subject is ready to enter its initial testing phase.

"But, how can we test it with the damn government constantly looking over our shoulder? The only way to test the specimen is by using it on a human being."

I ask my supervisor, a bit annoyed at all these stupid rules and regulations.

"This, my friend, is where you come in. We have a plan in place to test it on a human being. More specifically, we want you to test it on your roommate."

"My roommate?" I say, a bit shocked and intrigued. "How would that work?"

My boss smirks a bit mischievously and says "we're prepared to give you all the funding you require to properly test it in different scenarios, with different forms of stimuli. The symbiote has a failsafe built-in, should the subject ever grow too big, or out of control, he needs to either cum inside you, or you inside of him. Don't ask me how it works, the egg-heads insisted that this would be the best way to ensure a proper working fail-safe, it will shrink him back down to his original form, and he shouldn't remember any of it, or at most he will think it was all a dream."

After a few seconds of thinking, I put both my hands on his office table and ask "When do I start?"

Hello, this is a little prompt I would really like to play out with someone, where we're both roommates and have been for quite a while (so we trust and know each other) however, one of us works at a laboratory where they just finished the creation of a symbiote that, once ingested can transform the person into that from which they receive the most stimuli. So for instance, if a male person had fish for dinner they might (unknowingly) take on a few cat-like traits (sharp teeth, slitted eyes, cat ears etc). then, when they decided to take a walk outside and find a cat, only to have it scratch them as they tried to pet it, they might turn into more of a cat, growing multiple sets of breasts, a tail, meowing, going in heat, the whole shebang. After the transformation they will find that it's very hard to think, their new instincts telling them to fuck (or be fucked). But the symbiotes have a bit of a will of their own, causing the infected person to continue to grow, leak and cum their brains out unless another person gets involved to try and gets them off.

If you like this idea, feel free to message me! We can use reddit messages, kik or discord, whatever works for you. Mind you that most of my favourite tfs involve heavy feminization, futanari/sissyfication and also a few where certain parts grow so big you might become immobilized.

I should also note that I love a slow transformation. Where you first start to feel a bit hot, certain parts feel a bit sensitive, but you write it off as maybe an allergic reaction, or coming down with something. And slowly but surely your resistances cave until you're a slave to your instincts.

My kinks are: inflation, expansion, feminization, futanari, lactation, anthrofication, multibreasts, animal parts(hooves, udder, claws), monster girls, bimbofication, soft mind control/influencing, latex/rubber, excessive amounts of cum, submissive and dominant behaviour and probably a whole lot more.