Matou Zouken sneered as he looked down upon the pair of corpses being steadily devoured by his worms, the very least they could do to reimburse him for his losses in their little squabble. He did make sure not to have the crests consumed, those could prove useful for something.
He stamped his cane on the ground and tore the mystical defenses on their workshop apart. They were a bit better than expected, but still nothing remotely impressive. He had seen and dealt with far grander in his youth.
He stepped into the workshop and a swarm of worms left his body to search every last inch of the place. The Kuruoka had finally pushed their luck too far with him and now their family was in ruins. Which meant he was free to loot them to the ground. It had been some time since he had done so. It was a bit refreshing.
Information filtered into his mind of what his worms had discovered. Not too much worth noting. The materials could be useful while the research was novel if anything.
He then paused as a few of his worms found something interesting. He walked over and began to review the research.
His wrinkled grin was wide as a cackle left him, "Kehahaha! Missing one final piece! No wonder you pushed your luck you fools."
The Kuruoka had stumbled upon some very fascinating microorganisms from South America. They believed that by stealing his research they would be able to adapt their family's magecraft into something actually impressive.
They would be correct.
And now it was in his hands that they pushed their meager luck.
His wizened mind spun with ideas to make use of this research. His latest descendant was a waste. Shinji had been born with magic circuits due to his mother's status as a Carrier. The magical virus she carried was of little note, unfortunately. They had guaranteed her child would have magical circuits but they had been duds. The highest quantity and quality of magic circuits he'd seen in one of his descendants in centuries, enough to rival the heirs of some of the greater magus families, all for them to be impossible to activate.
He had researched a few methods but they proved too costly or weren't feasible with the weakening mystery of the Modern Age. So he had written the child off, apart from his use as a breeding stud later in life. He had potential but it was forever locked away. If he was in luck then a child of Shinji's would have better potential for sorcery.
If only that fool Kariya wasn't such a pathetic waste then the Zenjou would have been birthed an excellent heir! That damnable Tohsaka didn't know what kind of prize he had won by marrying that Zenjou! But no use in wallowing over the failures of his rubbish descendants.
Now he could have a method to turn a waste into something useful. Both for Byakuya's wife and her son. The woman would have served to feed his familiars but he had a proper use for her. Better than warming the bed of his pathetic drunk of a 'son'.
His mind full of ideas, Zouken made arrangements to loot the Kuruoka's workshop to the ground.
Their home was empty by dawn.
Months had gone by as he refined the… passable research from the Kuruoka into something actually useful. He imagined such work would have taken them years even if they had managed to steal his work.
His tests on Byakuya's wife, Rinko, had progressed steadily. Apart from the slight growth of her feminine characteristics for some reason, he could only attribute it to her magical virus reacting to the modified microorganisms in an unexpected but benign way. Despite those side effects, her potential as a magus had improved a fair bit. The effect would be much more profound on a child, but to take the spawn of a 3rd rate trash and make her passable was impressive. He had taken to teaching her enough magecraft not to kill herself. It would be a waste now that she was useful. It would also prove useful in the case Shinji died, she could teach her next likely more useful spawn and save him some precious time.
Apart from his research going well, he actually had a decent run of luck since his pillaging of the Kuruoka, that fool Tokiomi gave him one of his daughters! Little Sakura was undergoing training in his pits so that she could be a suitable 'heir'. If all else failed and Shinji survived but was still unable to practice magecraft, then she would make more than a suitable womb for him to impregnate in the future. He had to ensure her traits as one with Zenjou blood would be maximized. Her mother clearly had inherited the family trait strongly if Tokiomi's daughters held so much talent. So her daughters would have likely inherited that trait. But he had work to do to ensure that she did.
He could do without that wastrel Kariya moaning in his ear about the girl. He was such an annoyance he 'humored' his request if only to shut him up. He would train the waste to be the Matou Master in the upcoming Grail War and if he won -which wasn't likely- he would release the girl. Kariya proved to have little talent so he took to using his worms to 'teach' Kariya's body magecraft while he busied himself with more important matters. The way the failure writhed on the ground as worms crawled under his skin and ate his flesh was amusing at least.
For Zouken this was probably the busiest he's been in decades. But he handled the workload with little issue.
Two months before the Grail War he finished the modified virus. If it worked as intended, then Shinji's magic circuits would be forcibly opened and then amplified over time by the magical virus. This would take his theoretical magical talents even higher and he would finally have a suitable heir for the first time in centuries.
That or it would kill the boy. However, it was unlikely as he used the boy's mother's own magical virus as a basis to stabilize the microorganisms.
But if it did kill the boy, he still had enough of the unique microorganisms to try again at least two more times. Rinko had also been oddly randy as of late so if need be if Shinji died, he would just have her get pregnant with either Byakuya's or Kariya's seed. He would be free to try again with the next child.
He loaded the virus into one of his modified insects and went to see his grandchild.
Matou Shinji nervously fidgeted in his room. His grandfather asked to come in a minute ago and he of course obeyed. His wrinkled face was as intimidating as ever and the young boy did his best to stay calm.
Zouken beckoned him to come closer, "Come here Shinji. I have something I want to give you."
Shnji swallowed and said, "W-what is it, Grandfather."
"Hold out your arm." His grandfather said without answering his question. Shinji obeyed and held out an arm. The moment he did he felt a sting of pain!
"Ow!" He yelped as his arm was held like a vice. The boy couldn't help but watch as a strange bug pumped something into him! Soon heat began to spread out from his arm.
His bug stopped and Shinji felt very dizzy. He fell backward onto his bed and sweat began to pour from him as an intense heat filled every inch of his young body.
"G-grandfather… w-what… was that?" He said in between labored breaths. His lungs sucked in great amounts of air as his blood pounded in his ears. Darkness began to encroach upon his vision and the young boy's mind whirled!
His grandfather looked down at him with an appraising gaze, "Something that may help you practice sorcery. Do your best to ride this out and you will have what you have always wanted."
Even as what felt like liquid fire roared through his veins those words brought a smidgen of relief. Through grit teeth he replied, "T-thank y-you Grandfather…"
With those words, the pain within him magnified a thousandfold. He couldn't even scream as the pain of his body breaking down knocked him unconscious immediately.
The young boy's body spasmed and flexed as the magical virus modified with Divine Filament infected him. It had a strange reaction with the boy's variant of the original virus he inherited from his mother. The modified virus mutated into a more powerful form and began to rouse the Divine Filament from his hibernation.
Microscopic black tendrils began to invade and change the cells of the boy's body as it followed the programming instilled in it by the Magus. The Divine Fillament dormant for so long followed the command, to a much greater extent than what the Magus had likely intended or thought possible. It searched for what it was familiar with in the boy's DNA. It searched for the strength that humanity had in the Age of Gods. It dug deep and removed any troublesome 'junk' it found on the way.
Once it found what it was looking for it began to integrate it. It would take time to fully bring it to the surface. But nevertheless, some changes began to take place.
The first changes were physical. Skin, muscle, bone, and everything in between started to become simply better. So the boy would have skin that was paradoxically soft and supple but strong enough to defend against the claws and teeth of smaller Demonic beasts, muscles powerful enough to lift and crack stone to build rudimentary shelters, and bones durable enough to let a child withstand the harsh and untamed Age of Gods. Every organ was enhanced to perform at a greater level, the heart and brain in particular.
Then the priorities from the boy's original virus became apparent. The boy's small childish foreskin-covered penis and small balls pulsed. With every puled flesh rippled and grew. Large prominent veins pumped more and more virus-laden blood into the organ as it grew. The boy's modest thin two-inch penis throbbed. Two turned into a thicker three inches and then into a decently girthy four, then a thick five inches, which further grew into fat six inches, then seven inches, eight inches, nine inches, ten inches, eleven inches, and finally slowed at a monstrously thick 12 inches. The whole foot of pulsing shota cock looked positively gigantic on the eight-year-old's small frame.
The boy's testicles weren't left untouched. The small sack filled with marble-sized testicles pulsed as they grew into larger monstrously potent cum factories. They churned and gurgled with a level of virility rarely known to modern man.
Then the magical changes took place. The virus struggled for hours as it attempted to awaken the boy's magic circuits… but after the sixth hour, it succeeded. Magical energy flooded the boy and the magical virus immediately went to work. Soon the unnatural spiritual organs were enhanced for greater power generation and output and at the same time they became seamlessly integrated with the boy.
No pain shall come from performing miracles, as if it was his right to do so.
Shinji's sleep was fitful and his dreams strange. Various women surrounded him, their faces a blur. But their bodies were not. They reminded him of his mother's body… just more appealing. Giant sloshing breasts that are two times bigger than their blurred head. He just wanted to sink his hands into them. They leaked steams of breast milk from their fat nipples and he wanted to bite and drain them of wonderful milk. Big rounded heavily pregnant bellies filled with his children. Wide grabbable hips and massive wobbly asses that he wanted to sheathe his monstrous throbbing length between.
He could not see their faces but he could tell they looked at him in worship and he liked that look.
"Please bless us with your god cock and your divine seed Master!" They shouted as one.
And then he woke up.
Shinji shot up and his eyes snapped open as he breathed hard. He then felt sticky. He looked down to see he had shed his clothes at some point. But more importantly, he was coated in a thick layer of strong-smelling white gunk.
And it wasn't just his body, but everything! His bed was practically flooded with the sludge!
Then he felt something drip onto his outstretched hands. He looked up to see the white sludge dripping from the ceiling!
It was then the door to his room opened to reveal his mother, "Shinji are you… all right…"