Like, let's say these are just pretty normal, run of the mill grubs. They aren't in your brain. They aren't flooding you with any chemicals or hormones. They just... stretched open your greedy cock and starting squirming inside.

Maaaaaaybe you didn't notice or realize at first, pounding this stranger for all they're worth. Maaaaaaaaybe something in your brain said "Stop! Pull out-! Hnng- something's hnn- happen-nng!" But you didn't stop. You liked it too much. Whatever was rubbing your cock from the inside, stirring up your balls like that's what they were made for. At most I could see you being surprised when you pull out and there's barely any cum leaking from their puffy hole... you were feelings so good, your load should've been huge, but there's barely a trickle...

Whatever... you clean yourself up and head off, weird how hard your cock still is though. Not to mention your balls seem bigger than they were when you started... hnnn, what happened?

Maybe you take a bus home, stumble all the way to the back row so you can investigate with as much privacy as public transit can allow. You pull your waistband down and your hard, now oddly shaped cock flops out. That wondering squirming gets more intense and your eyes roll back briefly, what is this? With out thinking you fondle your shaft and can feel the movement under your palm... You should be scared. Most people would be, but a weak, wobbly smile crosses your lips as you squeeze and-

Is that... a grub? You stare at it dumbly as it wriggles on your thigh. You squeeze again and few more clog up your opening, bodies stuck and struggling against each other making your nuts growl. Fuck that's good. You were going home for the night, but how can you? You need to nut and clearly the only way you can dump these little guys properly is by being balls deep in someone...

Maybe... maybe, you were planning on telling them, right? That's what you told yourself as you staggered off the bus and into one of the only still open bars, falling all over a drunken stranger who looks about as desperate and sloppy as you. You were gonna tell them at the bar, but the music was so loud... so you were going to tell them in the alley, but there were some guys nearby having a smoke, and once they left, you were going to mention it then, but what would you say? "My dick is full of maggots, I think, let me smash?" And before you could convince yourself fully that getting consent for this was the right thing to do, this stranger had already grabbed your aching, fucked up dick and had your tip lined up with their slit.

You rammed inside, to the hilt, sweating, panting, letting yourself become worse, more broken. Ruined by the delicious, horrible sensation not just forced onto you, but that you knew you were forcing onto to this other person. Fuck it made it so much better. You imagine how it would feel for them, the soft bodies wiggling deeper into their womb, their ovaries, would they ever be able to get them all out? Would they subject their self to a doctor's visit? Would they succumb to the sick pleasure like you did? Who knows but one thing is for sure, you've never felt this amazing while fucking before, the knowledge that you're forcing something like this inside an unsuspecting stranger has you hard enough you could black out if it wasn't for the mind-bending ache in your balls keeping you grounded...

The best worst part is that the grubs aren't to blame. They've done nothing to change you biologically or mentally. This is just you. Something you've fantasized about. Something you want. That just makes it better. Hotter. So insanely good you bust what feel like liters into this person, who you promptly leave in that alley, limp and breathless. Fat grubs burying themselves deeper into their tender body.