In the Hoenn region, wild Taillow's were hopping along route 101, searching for food. They flew away, disturbed by a human walking towards them. The human's name was Rai, he was 16 years old; on his right shoulder sat his best friend and first Pokémon, Eevee. Rai and Eevee were on their way to Littleroot Town to visit Professor Birch.
"It's been a long time since we were last here," Rai said.
"Vee!" Eevee nodded in agreement.
"I can't believe it's been six years since I first started my journey with you. I still vividly remember when we first met." Rai recalled.
Rai had meet Eevee in Littleroot Town when he was ten. Even at that age, he was a brilliant strategist. He always won any game he played, from cards, to chess, to risk, to videogames—even when his opponents were 10 years older than he was. He was more of an introverted child, preferring to listen and observe during conversations, rather than participate in them. He often could be found sitting in a tree on route 101, just thinking. Because he didn't talk much and often wasn't in Littleroot Town, he didn't have many friends and the fact that he won any game he played didn't help either. He couldn't get a Pokémon from Professor Birch yet because he hadn't turned 10 yet. One day, when Rai was on his way to his favorite tree in route 101, an Eevee came running along the main path and, not seeing Rai on account of looking behind its shoulder, crashed into him, knocking both of them to the ground. When Rai regained his senses, he saw three Mightyena running toward him. He realized instantly that they were chasing the Eevee, but now that he was in their path, they would target him as well. He couldn't outrun the fast approaching Mightyena, he didn't have any Pokémon of his own to defend himself, and climbing a tree would prove to be a temporary solution at best. He knew he had to fight.
"Eevee, I don't know who you are or where you came from, but neither of us is going to live much longer if we don't do something," he said, knowing that the Eevee couldn't get away having lost as much ground as it had, "We will have to battle together to survive."
Eevee nodded and took up a fighting stance, its left front paw in a forward position and the front of its body in a crouch.
"Steady, steady." Rai said, waiting for the right moment to have Eevee attack.
"Wait for it…"
"Now," he shouted, "Rebound of the tree to your left and tackle the Mightyena on the left!
Eevee did just that and hit the left Mightyena on its jaw bone hard enough to knock it out and knock the middle Mightyena off balance.
"Now, jump back and do the same using the tree to your right!"
Again, Eevee did as Rai said and hit the right Mightyena in the jaw with perfect accuracy, knocking it out; however, the middle Mightyena was ready and leaped back, crouching, as Eevee landed.
"Eevee, slash his feet with tail whip and hit him from below with tackle."
Eevee ran toward the remaining Mightyena, but as it came close, it stutter-stepped, making the Mightyena react too soon, jumping. Eevee slid underneath it, but instead of tackling the Mightyena, it stuck its tail up, pointing at the Mightyena's chest.
Rai was shocked at what he saw; Eevee's tail had turned into a shiny green leaf, a razor sharp leaf that looked rather like a blade! The Mightyena fell on top of the tail, driving it partially into its chest. Rai looked on in amazement as Eevee's fur bristle and he saw electricity shoot along Eevee's tail and into the Mightyena, shocking it into unconsciousness. Eevee pulled its tail out and then the tail transformed back into its normal, fluffy shape; and its fur smoothed out.
Eevee ran back to Rai, who was stunned at what he had just witnessed, an Eevee that could use the high level attacks of two of its evolutions, Leaf Blade and Thunder.
"Nicely done Eevee!" Rai said. "That was amazing!"
Eevee grinned and proudly said its name, "Eevee."
Rai grinned also, then asked, "Where do you live Eevee?"
He had never heard of an Eevee living in the Hoenn region before.
Eevee sadly lowered its head and mournfully replied, "Veee."
"You don't have a home?"
Eevee shook its head.
"Would you like to come home with me? I'm sure mom and dad would let you live with us."
Eevee lifted its head, eyes shining, and happily replied, "Vee Vee!"
"Alright!" Rai yelled excitedly. He kneeled on the ground and Eevee jumped into his arms. Rai started running back home as fast as he could.
On the way back to Littleroot Town he asked several questions; in this fashion, he found out that Eevee was a female and wasn't native to Hoenn, but instead came from the Kanto region. He also had begun to look closer at Eevee's features. She looked like a normal Eevee, except that her back left paw and leg were a light tan and blue color (almost a milky-tan), her mane and tail tip were pure white, and her bangs were longer and slightly tilted toward the left side of her face, obscuring half of her black eye.
He arrived at his house, opened the door, and promptly asked his parents if he could keep Eevee. They were delighted their son had finally found a friend and immediately said yes. Since that time, Rai and Eevee had been close friends.
Through subsequent conversations and the help of Professor Birch, Rai learned that Eevee had been evicted from her tribe because of her unique abilities to use her evolutions' high level attacks and her unique fur colors. She had wandered Kanto until she came to Fuchsia City. From there, she stowed away on a boat that had docked near Petalburg City. She eventually made her way to Oldale Town and went south into route 101. There she had ran into the three aggressive Mightyena and then crashed into Rai.
Through training with Eevee, he discovered that she knew the moves Leaf Blade, Thunder, Blizzard, Hydro Pump, Fire Blast, Psychic, and Moonlight. Her Pokémon ability was Adaptability, but instead of only powering up Normal type moves, it also powered up her evolutionary moves.
Rai and Eevee trained almost constantly, and Eevee proved to be just as good a tactician as Rai. The two were inseparable. Months later, Rai turned 10 years old and set out with Eevee on his journey to gain all the Hoenn gym badges and make it to the Hoenn League Tournament.