Prologue

The story of the Child-Who-Lived very rarely ever changes. James and Lily Potter are murdered by Tom Marvolo Riddle Junior, their child gets sent to live with Lily's sister, only finding out about magic when the Hogwarts letter arrives. However, Senna Dorea Euphemia Potter was not normal, even by the standards set by her counterparts, male and female. In one bout of accidental magic when she was five she literally shifted dimensions, her cousin Dudley had been given Pokémon Red as a gift. Senna fell in love with the creatures, she had been born July 31, 1990, ten years after some of her counterparts.

Arceus and the other legendaries would have sent her back immediately had Dialga, Palkia, and Celebi not seen how her life had been like plus what it would be like. Instead they decided they would allow her to stay, help her all they could by procuring her books, and send their own Chosen One back with her when she would have to relive ages eleven through seventeen. Senna was taken in by Blue Oak, the father of Daisy and Gary Oak. Daisy adored having a little sister even if she preferred hanging out with Delia Ketchum's son whom she kept closed mouthed about whom his father happened to be.

Chapter 1

Senna Oak stumbles down the stairs at her grandfather's lab, glaring venomously at her brother. Gary was quick to hand her the strongest tea she was allowed to have, and immediately refilled the mug, the red head with hazel colored eyes was still glaring at him evilly, " I'll get you a female Eevee if you don't prank me for waking you up this early. "

" Throw in a female Vulpix and Zorua too, then I may just forgive you. " Senna snaps at her 'twin' brother. They all knew she was adopted, hence why she got along better with Ash. Senna yawns and with Gary letting her lean on him makes it into the lab.

Professor Samuel Oak chuckles, " Here's your national pokédex in red and gold like you asked, every region is in there, every variety of pokéball, twenty of them since you beat me at Poker, along with ten of each evolutionary item, copies of every book you've borrowed from me, copies of your cookbooks for life in the wild, two PokéGears, two egg cases, a poke flute, red flute, yellow flute, and blue flute. You also have a Berry Case and fifty of every type of Berry, forty each of Potions, Super Potions, Hyper Potions, Max Potions, Revives, Max Revives, Restores, Full Restores, Fresh Waters, Soda Pops, Lemonades, Moomoo Milks, Ethers, Max Ethers, Elixirs, Max Elixirs, Burn Heals, Freeze Heals, Antidotes, and Paralyze Heals. You also have every type of fishing rod as well. "

Senna smirks, " Pleasure doing business with ya, Gramps. "

Gary starts banging his head, " Would you have done the same for me if I asked? "

" Maybe, Ash brokered a deal with me for the egg case and PokéGear. " Senna states.

" What did he trade you anyhow? " Gary asks.

" He'll supply the tents, sleeping bags, and Repels plus I get a travelling companion that I won't be tempted to strangle for being an Arceus be damned morning person. He's also supplying the cooking equipment and my caffeine. Delia thought it was a fair trade since I'm going to go fishing with Ash before we leave. " Senna states.

" Sis, if I promise to play nice with Ashy-boy will you let borrow your Old Rod to catch a Magikarp? " Gary asks.

" You buy for me in Celadon City, I'll give you a list, that includes the female only items as well. " Senna says.

Gary shudders, Senna happened to be an early bloomer, thankfully Delia had given her the Talk, in exchange Blue had handled Gary and Ash at the same time. " Fine, Dad gave me a PokéGear as well, text me the list. "

Senna nods, Gary chooses Squirtle as his starter while Senna had put in a call to the Alola region, and gotten a Litten for herself. She fully intended to catch a Pidgey just as soon as she could. " Give me that Pikachu you recently caught, Gramps, something tells me he and Ash are meant for each other. Meet us as the water and bring my bag, bro. "

" Ah, Senna, ya might want to change first. " Gary says.

Senna blinks as she looks down to see her pajamas. Senna sends another glare his way, " Why did you have to wake me up so damned early? "

Senna heads back upstairs, showers, changes into orange denim shorts, an orange halter top, black sneakers, black fingerless gloves with orange cuffs, her red hair was pulled back into a ponytail while she puts on a black Team Umbreon Cap. Gary blinks when she comes back downstairs, already having her fully packed bag on his shoulder, he may have to have a chat with Ashy-boy before he took off. Senna makes her way to the Ketchum home before grabbing a bucket of water, walking up the stairs, and dumping it on Ash. Ash surges upwards, spluttering, even as Senna tosses him a pokéball, " That contains an ornery Pikachu, win him over, he's your starter. "

Ash had long since learned that Senna just had feelings about these type of things, like Gary he realized that he was going to be very busy curb stomping idiots if Senna was going to dress like that. It didn't help matters that Senna was already starting to develop a bust at ten. Ash may play stupid, but that was only so people underestimated him. He'd have to stake his claim before any idiots went after Senna. Senna leaves him be to get dressed and work on winning over his new partner. Once dressed and having won Pikachu over, helped when your pseudo girlfriend happened to be a psychic, and trained you up, he grabs his green backpack, eats a good and hearty breakfast made by his mother, Gary and Senna were both over. Ash smirks when he realizes Gary wants a Magikarp, Gary holds Ash back while Senna goes on ahead, " Keep the perverts away from my sister. "

" They'll be curb stomped, you honestly think I'm going to let any of those idiots out there get their hands on Senna? " Ash asks him.

Gary blinks, " Son of a bitch, you've been playing stupid this entire time. You plan on claiming her for yourself, don't you, Ashy-boy? "

" Hell yes, Senna's mine. Mom already knows I plan on her officially being my girlfriend once we're in our teens. She's already my pseudo girlfriend, mostly because she uses me as her fanboy repellant. " Ash states as they walk after Senna.

Gary blinks at this, " I really shouldn't be surprised by this, should I? "

" Nope, there's a reason why I want her travelling with me, I'll feel better if she's where I can help her if need be. " Ash states.

Senna had already caught a Magikarp, Tentacool, Chinchou, Poliwag, Goldeen, Staryu, Shellder, Horsea, Krabby, Psyduck, Slowpoke, and a migrating Carvanha by the time they caught up to her. She gives them the rods while she works with her new pokémon. Only her Magikarp and Tentacool would be coming with her along with Litten. She'd call for Tempestia after beating Brock in Pewter City. The boys both catch Magikarp, Chinchou, and Tentacool while Ash gets a Poliwag and Gary a Goldeen. Gary splits off from them since he would be going around in a car, the lazy bum. Gary at least could rest easy in knowing Ash would watch over his sister. Even if the odds were good once they were old enough Ash would waste no time in fully claiming her.

After leaving some of their pokémon behind Ash and Senna set out on Route One. The female Oak was quick to catch a female Pidgey she names Gusty with the Ability Keen Eye and the egg move Tailwind. With Chinchou's help Ash catches a Rattata before they move on, Pikachu has his cheeks sparking in warning to the area Spearow flock. Senna quizzes his knowledge one the major Kanto gyms, their leaders, and specialties while they meander their way to Viridian City. They had the pokémon they could have out so they could work on their stamina and endurance. This was a really good thing for Gusty and Rattata as they were at such a low level.

Gusty would be helpful at the Pewter Gym as would Ariel. Once they stopped for the day they would train their pokémon and themselves. Little known fact to the Oak family was the fact that Ash had been taking martial arts lessons for years in order to help with his klutz attacks. Ash had taken to teaching Senna since he had actually reached master status in his discipline of Martial Arts. He was very much enjoying the amount of skin Senna was showing too.

" You do realize that I only wore this because of how little the odds were of actually running into anyone else, right? "

Ash blinks and looks at his pseudo girlfriend, " You're going to change into something else before we get to Viridian City, aren't you? "

" Naturally, plus, I wanted to see how you and Gary would react. " Senna admits.

" Save these kind of outfits for me. " Ash states.

" Only if some slut doesn't piss me off. "

Ash winces at the reminder of the 'Incident'. A girl on a field trip by the name of Giselle from Poké Tech Academy had pissed Senna Oak off royally. Giselle had gone around using her looks to get the boys to do anything she asked. If Giselle hadn't targeted him Senna would have left her alone. Instead Senna had gone full on bitch when Giselle tried her tricks on him. Gary, by dint of having two older sisters was somewhat immune, not to mention the fact that Giselle had known better than to mess with Senna's brother. She hadn't known that Ash happened to be her pseudo boyfriend. Senna was very possessive of her friends and family, in particular Ash.

Ash couldn't wait until they hit their teen years and hopefully they remained with only themselves for travelling companions as well. No chaperones would mean they could have a lot more fun together. Until then they could snuggle up together at night, they had gone on camping trips for purely that purpose after all. Once they get their camp set up for the night Senna finds a nearby stream and starts training her pokémon. Poseidon was working on Bounce while Ariel works on Poison Sting and Water Pulse. Ash has his Tentacool also work on Water Pulse. Once they're sure their pokémon are set they start sparring before cooling down. Senna sets to work on making some food from the surrounding flora.

Ash has Pele help him make some calming tea so they could get to sleep easier. The pokémon would be left outside their balls so if they were attacked they would have some warning though Ash does send Pikachu off to use his Lightning Rod ability. Delia had sprang for water proof tents even though they only set one up and zipped two sleeping bags together.

Senna:

Pele- female Litten

Poseidon- male Magikarp

Ariel- female Tentacool

Tempestia- female Chinchou(at Lab)

Tethys- female Poliwag(at lab)

Arista- female Goldeen(at Lab)

Attina- female Staryu(at lab)

Adrina- female Shellder(at lab)

Adella- female Horsea(at lab)

Percy- male Krabby(at lab)

Tobirama- male Psyduck(at lab)

Shikamaru- male Slowpoke(at lab)

Oceanus- male Carvanha(at lab)

Gusty- female Pidgey

Ash:

Pikachu- male

Magikarp- male

Chinchou- male

Tentacool- female(at lab)

Poliwag- male(at lab)

Rattata- female

Gary:

Squirtle- male

Magikarp- male

Chinchou- female

Tentacool- female

Goldeen- female

Disclaimer: I do not own Harry Potter or Pokémon.