Kuro (FGO) x PoV
JADF
Kuro pulled her pristine futa cock away from the slippery, cum drenched hole that was your cumdump sleeve of a cock. "How about another round?", she asked with a confident grin decorating her face. The perverted holy grail wish truly had replaced her life sustaining necessity to consume mana to even greater need to dispense it. "Just give me a moment, I'll be back up in no time!"
And just as she said that, her balls were already subtly growing as they produced more rich cum with an otherworldly aura that you could sense without really seeing it. At first they were apple sized, then cantaloupe sized... Her breathing grew heavy and desperate and she had a crazed glint in her eyes. Her panting moans became small yells. Her sweating, brown ballsack was starting to weigh and push against her thighs as the balls inside them reached watermelon size each, stretching the sack to new limits as the tightness revealed strained veins under the throbbing surface.
Kuro's flustered gaze turned to you like a predator would towards their next prey. "Haah...! Give me that!" She pounced over onto your lap, easily pushing you back down against the bed with her servant strength. Her trembling hands could barely align the tips together, made worse by her involuntary little thrusts. Kuro grunted in frustration until her precum drizzling tip finally found the slightly gaping mark. This time she didn't enter with any gentle insertions but instead shoved it in as deep as it would go, so far in fact that it pushed at the back of your prostate! Kuro arched back in ecstasy as her balls twitched up and down in anticipation. Then it started again... How many times has it been now, you pleasantly wondered.
Clearly she wanted to piston you as fast as her lust demanded, but the sheer heft of her balls were actually forcing her to limit her speed into merely fast pulling and pushing, which was clearly testing the limits of her patience. Then you started noticing something. Her hands that were sticking to you were forming circuit-like magical patterns, spreading to her arms and onto your body. "Haah... ohh... I can feel it", Kuro muttered against your chest as she was still thrusting in and out of you. "This is spell new even to me, but I can tell what this is... My mana is becoming attuned to you! Hah, haahh...!! Master! This is dangerous! We need to stop!!!"
Kuro threw herself away from you and stumbled a few steps back, quaking and throbbing with a painful arousal. "The mana inside me has changed in its properties. If we were to continue, I can feel my sperm would surely inseminate yours." She clenched her fists, her face tormented by regret. "I'm sorry, I just... my desires got the best of me! I cannot continue carrying out your fantasy! I'm sorry, master..." This may have looked a bit more dramatic if she hadn't already started jerking off, but it was understandable given how much heat she was in already.
But then she dared to glimpse at her master again who was - much to her surprise - smiling.
"Master...?"
"By the order of command spell, I order you to be overcome by lust towards me."
"Master!?! No, what are you--"
"By order of command spell, I order you to cum inside my urethra."
"Master, stop!!!"
"By the order of command spell, I order you to impregnate me."
"Mas-...."
Her desperation to be mindful of her master's safety turned into desperation to breed. It's like she wanted to say "Now you've done it", but she couldn't even muster that. She simply ran her eyes down to her cock and then back to you, and then leapt onto you. Although Kuro was still trembling with unseen arousal, the movements she needed to carry out her task were made precise by the command spells' magic. Swiftly she aligned the tips against each other, and immediately resumed the thrusting she had quit before. Perhaps it too was the command spells' effect, but she was able to put out much faster pace without feeling uncomfortable at all. Her fervent thrusting was reaching so deep now that it was prodding the openings of your vas deferentia, switching between the two and ramming them loose.
"HAAH...!! HAAH!!", Kuro grabbed you in a tight hug as she embraced you for one last hurrah of thrusts, each violently slamming you against the bed at utmost speed and pace. At the same time on her heavily swinging balls, there was forming a new kind of magical crest that you hadn't seen before. "Hah! Ah! Ma-...! Master... do you know how many sperm are in a normal human ejaculation?" Kuro abruptly quizzed you as she summoned her conscious back one last time before the inevitable happened. "100 million sperm!! Guess how many that makes when... Ah!! AHHHH!!! NNGAAH-AAAH---!!!"
She pushed in one last time as huge balls clenched up, forcibly spreading her thighs with their sheer size. Her hips were still squeezing the tip against your prostrate until the top of the glans reached and completely blocked the opening to your bladder, leaving only one direction available. Immediately, a hot splash of the richest cum surged straight into the two gaping openings of your prostrate, giving a sensation of expanding warmth that looped around towards your vulnerable testes, each pulsation pushing the advancing torrent closer until it hit the bottom of your epididymides. "Sloorm, sluurn, sloorm", Kuro's cock continued to shoot out and build more pressure until the final inner openings of your reproductive system caved in. Within your balls a new hot warmth bloomed as Kuro's semen invaded and spread inside the seminiferous tubules, quickly filling them with virile swarmers.
But Kuro wasn't done, eyes rolled and hot muffled breath suppressed against you, she continued to twitch in a standstill as her sack still kept pumping out seed suspended on the top of her sack.
By the time your sack had grown many times their original size she finished her ejaculation and finally started regaining her confident composure. "If this is what the master wanted so badly, then who am I as your servant to deprive you of it? Take this!" Kuro smugly started thrusting again, but it seemed more out of her own natural volition. "How is it, Maa~ster ♥? You still want more, right?" Her thrusting became faster and her breathing turned into moans again.
"Here it comes again! Take it! GET PREGNANT! NNHH--!!" The already flooded canals of your ejaculatory ducts spiked with pressure once more as even more of Kuro's cum was being forced in. "Ba-dum, ba-dum...", your balls' growth matched the steady spurts of Kuro's climax. Groaning and sloshing in protest, they were now engorged far beyond utmost fullness with Kuro's virile seed. Within that whirlwind of mixed cum that now churned inside your balls, the vastly outnumbering Kuro's sperm were hunting down every single one of your sperm, several of them simultaneously entering for each one of your swimmers. The drastically erroneous mix of chromosomes would be a far cry of anything even resembling a humanoid, but where this would have killed the resulting failed zygote, here they were forced to kickstart the cell division stages regardless, resulting in genetically unstable mutant morulae. These then quickly attached to your walls of your septa in the billions, sealing the countless new growths in their unorthodox "wombs"...