William's mother was killed by a villain. luckily he survived. His father was an unknown and his mother's family wanted nothing to do with him.
William was left at an orphanage. He had a quirk from birth. Whenever he touched someone he could tell how strong and how much quirk factor someone had.
He could pull on them and like grains of sand, the quirk factor would trickle over. over time he would instinctively understand the samples he'd taken. Their components and how they'd react in combinations.
He learned to nurture samples to make them grow. it would not make them more powerful, just in larger amounts and more stable.
He watched how the quirk factors of the other orphan children coalesced into quirks. like clouds of color becoming stars. some had more than one but most just had one.
One child came in without a quirk. But William knew he had some quirk factor. it just wasn't enough to form a quirk. William nurtured it but it still didn't coalesce. Then he put in some quirk factors they didn't have and it formed. A star.
At the age of six, their quirk awakened. Air skin, allows the user to make a layer of air cling to their body. Useful for avoiding rain or diving underwater. Their parent's quirks were telekineses and energy shields respectively. He got a small portion of each and Williams added a small amount to control air.
The other orphans who had quirks still had unused factors. William theorized that different quirks among siblings were a result of combinations of quirk factors. what wasn't used stayed dormant.
The adult stars were brighter and larger but the clouds still existed. william wondered if it would ever get used. So he pushed it, forcing unused factors into the star of one of the caretakers.
She had a quirk that let her produce light from her hands. the quirk changed slightly, it started producing colored light.
William theorized that the heroes on tv who suddenly got stronger in a fight had this happen naturally.
William was about to turn five and decided to reveal his quirk before he was labeled quirkless. He showed he could copy quirks. He didn't show all it could do and claimed it was temporary.
Then a few kids got the quirks checked. Sometimes it's hard to figure out the activation for your quirk so its necessary.
Then William saw something entirely unnatural. Some of the kids came back without quirks. they were torn out by the root. The stars were gone leaving behind fragments like little embers. The embers were dying. they couldn't grow back and the leftover clouds weren't replacing the lost quirk naturally.
William could feel something there. traces of quirks. Not enough for samples but enough to be a fingerprint for if he met the owner.
At least three quirks were used. One for numbing, one for stealing, and something with bones. Not quite growing and not gluing. Fusing that's the word. Someone fused the pinky-toe joints.
William thought about remaking their quirks. The quirks wouldn't be the same since he didn't have enough samples of them. But also, whoever took them would surely notice if they suddenly got a quirk again.
Then William was adopted into the Aoyama household. he was to be Yuga Aoyama's brother. they were both 5 but Yuga still didn't have a quirk. The Aoyamas were waiting to see if he was a late bloomer.
William knew that Yuga was in fact not a late bloomer. Yuga was short on quirk factor. he barely had a puff of smoke in him. He also knew that the Aoyamas would be approached soon if Yuga's quirk didn't show up.
So William told a white lie, that Yuga has a quirk that he can feel it. Yuga was ecstatic teary-eyed. William explained that he can tell if someone has a quirk when he touches people. That he can't copy Yugas because it hasn't awakened yet and he doesn't know when.
William continued to collect samples from classmate stranger and relatives. His quirk grew in strength letting him collect larger samples and analyze them faster.
Before it was a few grains per minute and took a few days to identify their factors. Now it's a pebble a minute and about a day per pebble. It's still slow. But it takes far fewer samples to map out a whole quirk.
They're turning eight and Yuga still hasn't awakened his quirk. William had been gathering samples to custom-make yuga his own quirk
William remembered the quirk Yuga would have gotten, navel laser. He also realized that Yuga has shown no interest in anything French. Hypothosis. The naval laser Quirk came from a French guy or maybe a guy who really likes French.
William has stored a few quirks away. Some for an emergency and some are copies of quirks he plans to upgrade and impose on the originals, little boosts to give his future classmates an edge without being too suspicious.