Just to be clear, the main HP elements won't show up until the incident with Mewtwo. The idea of Aster confronting Mewtwo about his hypocrisy regarding the clones he made and the original versions is what sparked this idea.

Something terrible had happened. The world had ended at the hands of a fool, and this time the Champion was too far away to effect events so that the world would survive. To be fair, Ash was well into his fifties and was with his children and grandchildren at the time.

Arceus could not let the world be destroyed...so he decided to rewrite history and leave a special 'container' for Ash and Pikachu...with a few extras as thanks for all the times he had saved the world originally. Once Ash met his partner, he would regain a large amount of his memories from events yet to come in order to better prepare himself for the event that destroyed the world.

He concentrated fully on the 'package', using the help of Dialga and Celebi in order to make sure it was delivered correctly, that he failed to notice an outsider approaching.

This wasn't like the Pokémon that arrived from other worlds, like Deoxys. This was a human soul of great power and ability.

Arceus sent the package into the past, believing things would play out for the better this go around...completely unaware of the fact that the outside soul had collided with that of Ash and dislodged it from it's original course. Ash would awaken in his teenage form next to Sir Aaron, rather baffled as to what was going on.

Meanwhile the second form began to alter and rearrange the past to better suit it's own presence by instinct, unaware that it had usurped the body of the native Champion.

"Congratulations Mrs. Ketchum, it's a girl!"

Arceus would not notice the mistake for some time.

Professor Oak looked at little Aster with some concern. She had started sneezing with no end during the training camp he held for children every summer, and they couldn't figure out why. Considering she had trouble breathing, he was rather determined to find the cause.

The only thing he could think of was that she had an unusual reaction to the lesson that day, which was the effects of certain pokémon attacks such as sleep powder during battle.

To that end, Oak ran a rather standard test for allergic reactions. It wasn't something he did normally, but it was something all pokémon researchers learned to do in case one of their experiments caused a bad reaction in the pokémon they were working with. As luck would have it, the same tests were also the ones used for humans.

So you could imagine his surprise learning Aster Ketchum had a rather bad allergic reaction to the three common powders used by grass and certain bug-type pokémon.

Dahlia held her daughter who wanted to know why she had such trouble breathing during class.

"Well I have good news and bad news. The good news is that I've figured out why Aster was sneezing so badly. The bad news is that you have a rather unusual allergy," said Oak.

"Allergy?" said Dahlia.

"People and pokémon develop immunity over the coarse of their lives when exposed to certain elements. Much like how we give people vaccines to help combat the older diseases. Sometimes when someone is exposed to certain stimuli...such as canine or feline pokémon fur...their bodies produce a stronger reaction than normal which causes their body to reject the stimuli and create a bad response," said Oak. "Young Aster is apparently allergic to certain proteins that are commonly produced by the attacks known as poison powder, sleep powder and stun spore, which are often produced by grass types and certain bugs. It's rather similar to having a dust allergy."

Aster looked decidedly unhappy hearing that.

"Does this mean I can't be a trainer?"

"Far from it. It just means you have to be extra careful when battling against certain pokémon and have specific medication on hand in case they use it. From what I've been able to ascertain, your body has a rather bad reaction to the proteins."

That seemed to reassure the girl, however it did make Oak wonder exactly how common such a strange allergy was among trainers.

Three months later...

Aster was reading articles online, since her mom had a special lock on the computer to keep her from playing games. She had learned that while the computer would block games whenever she forgot to do her homework, it wouldn't block education sites like the ones where pokémon professors and researchers would post their latest findings about pokémon.

That was how she stumbled across an article about unusual allergies.

The surprising case of subject "A"

During a normal training camp for children, the subject of pokémon allergies was brought to my attention during a rather routine lesson about status effects during battle situations.

When Butterfree used Sleep Powder, Subject "A" began to sneeze uncontrollably for five full minutes and had to be removed hastily from the scene. A standard reaction test revealed that Subject "A" had an unusual reaction to the proteins found in the common grass moves known as Stun Spore, Poison Powder and Sleep Powder, and that normal medication for allergic reactions had minimal effect on the subject's condition.

Further investigation revealed Subject "A" also has an allergic reaction to the flowers commonly pollinated by grass and certain bug pokémon, who then use the pollen to produce those same three attacks.

I would like to inquire as to whether you have come into contact with any other trainers suffering from this condition and if it's possible to alter the standard allergy medication to better treat the condition. I would also like to propose a study as to other similar conditions to anyone interested.

Professor Oak, Pallet Town

Aster...had no idea Professor Oak was so bothered by her allergy that he wrote a paper on it. Most of the paper went above her head, but the letter alone said that she was subject "A" as he put it.

She scrolled further down...and found that she wasn't the only one who had an allergic reaction to the pokémon attacks. Apparently while it was an uncommon allergy, it wasn't a rare one. From what she read there was a rookie Gym leader in Pewter city who had a younger sibling who had that same allergy, and as a result was banned if any of the pokémon who could use those attacks came into the gym.

There was even a little girl who's parents breed Combee and Vespiqueen for their honey that were specifically bred not to use those attacks because she had an allergic reaction to the same proteins.

Heartened she wasn't the only one to suffer from an unpleasant allergy, Aster began to reach out to them.

So far she was only able to contact the girl who's family raised pokémon for the honey and the gym leader, but at least she wasn't alone.

Aster was quick to warn them both not to use any products produced by the Celadon gym, as the leader there used grass pokémon and was well known to use powders that were naturally produced by her pokémon in the products. She had found out the hard way about that when she knocked over some of her mother's make-up and it had gotten on her, causing a nasty bout of hives. Apparently there was enough of the proteins in the make-up to cause an allergic reaction.

Dahlia had thrown out the rest of her make-up and made a point to look at the ingredient labels ever since, as Aster had been almost bedridden for two full days after that.

Coincidentally it was that incident that spurred Oak into asking other researchers if they knew of anything that would work better than the standard one used.

It would take the researchers two more years, but by the time Aster was old enough to become a trainer it would become one of many "special" medicines for those with unusual allergies.

On the plus side, Dahlia was finally able to find make-up that wouldn't cause a bad reaction in Aster thanks to her friend with the Combee.

The farm the girl lived on was struggling to deal with a competitor, until Aster suggested using the wax and honey to make special make-up for those who had allergies like them. Once they figured out how, they ended up creating a special niche market that caused their farm to become well known to a lot of trainers.

After all, wearing the special honey line had a side effect of attracting pokémon without having to spread it on trees.

Aster now had a lifetime supply of the stuff, and was more than happy to be one of a select few who would get the new products before they went on sale. Her particular favorite was a perfume that smelled like Gracidea flowers.

She loved them so much she had them growing outside her window.

In an unknown space, outside of time

Ash woke up slowly wondering what the heck happened. One moment Arceus said he was being sent to his younger body with Pikachu, the next he was here.

It took him a moment to register the presence of Sir Aaron, Lucario and his brother Pikachu.

"What happened?"

"It seems someone was transmigrating into our world and their soul was mistaken for yours," said Aaron apologetically.

"Transmigrating?" said Ash confused.

"It basically means someone died on one world and is going to be reborn in ours. In this case, her soul was a close enough match to your own that when it collided with the work Arceus was doing, she took your place by mistake. Normally this wouldn't happen, but this was a special case," said Aaron. "From what I saw, she had a power similar enough to Aura that she might be able to use it on our world."

"What does this mean?" said Ash, upset.

"Well for now she's taken your place, so you'll be staying here until Arceus registers the mix-up. Depending on how things go, he might send you back anyway with a few additions, or he might attempt to erase her existence and perform a swap of sorts," said Aaron. "From what I've seen though, I don't think her presence is going to be harmful."

He had been keeping close eye since he realized the mix-up, and had looked at "Aster" closely. His best guess was that the soul inside was using this chance to get a real childhood they missed out on the first time, and had no intention of causing trouble. The girl was a very kind soul that had been born with great power.

She was unaware of it for now, but once she got Ash's memories, it was likely it would awaken some of the latent knowledge of how to use it.

Ash watched the replay of Aster's life played out, so similar to his own, but with major differences as well.

Aster enjoyed reading more than he did, and seemed to have an inner maturity that had taken him decades (and two children) to fully develop. She also had a musical knack Ash never attempted to mess around with.

Her relationship with Gary felt more like she was the 'older sibling' of the two as she was the only one in their age group who could keep his ego in check. Daisy and all the older women adored her because she was the most mature of the children in Pallet Town.

All too soon, the day he would have gotten Pikachu drew near.

Much to his surprise, the mouse pokémon Professor Oak found chewing on his cables wasn't his familiar partner...then again he wasn't sure what he expected considering Pikachu was right next to him.

Aster, it seemed, would be getting a female Pikachu. He didn't know whether it was another tweak to the timeline or a side effect of the fact that he had been born a girl this time around.

Either way, he felt comforted that he wouldn't have to watch his partner be trained by someone else while he was able to do anything.

Aster looked at the Pikachu that was the only pokémon Professor Oak had left. Which she found highly suspicious as she had woken up extra early and had beaten Gary here.

Still, she had no real problem with the electric mouse, and she was actually rather cute.

However she noticed very quickly Pikachu hated being kept in a pokéball.

Aster went eye level with the mouse.

"Look, the fact is that I have to have a pokéball for you. So I'll make you a deal. You don't have to go inside except for emergencies when I can't reach you quickly enough, and in exchange you don't try to shock me without a good reason and at least try to listen to commands. Deal?" she asked.

Pikachu seemed to consider the offer. Since this female had at least attempted to start off their relationship peacefully with the apple slices she had for whichever pokémon she got, she was at least willing to listen to reason. The deal was rather good, and it was a compromise for both sides.

Pikachu held out a paw.

"Pika," it said seriously.

Aster shook it...only to get electrified for her trouble. Pikachu snickered at her poofy hair.

"Okay, new rule. No electric shocks except for when I'm being stupid or for hilarious pranks," she said.

Pikachu nodded, all too happy to agree to that. She jumped onto Aster's shoulder and easily rested there.

It felt strangely natural and oddly nostalgic for Aster...however the nostalgia felt more like she was used to something a bit more feathery and less furry.

Dahlia was delighted to see her daughter's new pokémon. Even if she did get a minor shock from Pikachu. The firm flick to the forehead from Aster and the Look she gave her new partner put a stop to that though.

Pikachu would only come to respect her new human partner when they were confronted by a less than amused flock of Spearow attempting to come after them because another trainer stirred their ire.

The determined and unflinching bravery Aster showed when swatting the less than happy bird pokémon with a thick branch, despite the number of cuts she got from their beaks and talons earned Pikachu's admiration.

Not many human females would be able to withstand that sort of assault without trying to run, or look towards danger without any fear of being hurt.

Pikachu finally had enough of the birds, and sent a massive thunderbolt into the sky, causing them to fall from the shock...however the bolt strayed slightly and hit something in the distance, causing a shriek of rage.

Aster had to wonder if this was going to be a sign of things to come when she saw a Ho-Oh fly above the newly made rainbow from where Pikachu caused the clouds above to break away.