Fact: Adam made Leafy a vaporeon as it reminded him of his deceased brother's main  Pokémon, Dewott. Vaporeon is also my favourite eevee evolution along with Umbreon. 

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Marshall eyes lifted off the clock in his dash for the last time in his life, eleven thirty, it was later then he had had meant to stay out training with his Pokémon but when it came to it, he always lost track of time. Marshall was one of the few trainers that trained alongside his Pokémon every step of the way. If they ran, flouted, or flew a 10k he ran a 10k,  if they practiced dodging and aiming  he participated and encouraged them, if they punched old trees to strengthen their hits he put on some gloves and joined them.  It left him exhausted all the time without a doubt, but it was all worth it when he felt the adrenaline of a battle and commanded his Pokémon to victory. 

Normally he wasn't a fan of keeping his friends in their pokeballs, but after they had pushed themselves so hard they allowed themselves to be tucked away for a nice long and well deserved rest. He drove a black truck that let Scolipede sit in the box, the large bug type got a kick out of the wind blowing it's antenne around. Skarmory usually would fly alongside, while Haunter would mess with the radio and put on the weirdest songs it could find and Renuiclus would scold it and try to use psychic to change it back. Dewott would keep the peace and happily sing along to whatever song played. It was Dewott that had insisted on staying out of its pokeball, it slept in the passenger seat with it's head rested gently on the door. 

Marshall currently lived in Unova, the rest of his family including an energetic younger brother lived back in Kanto. He lived not too far out of town, in a lot that was big enough to let his Pokémon have room to run outside. One of the lights he could see dotting the dark hillside was the light outside his garage, a yawn escaping his mouth as he passed a sign that said he was not too far now.

But he never got home. 

He hadn't noticed the other driver driving behind him, in the other lane. He was driving faster then the posted speed limit, and Marshall didn't have time to react when the other driver suddenly tried to merge into his lane, maybe it was because he was drunk or maybe because his truck was black  and hard to see, it was a direct hit. Marshall felt his entire body slam against the door and heard tires screech. His first thought was Dewott's pokeball, maybe if he got the water type in there fast enough it would be safe. But there wasn't any time, the truck rolled, glass shattered, his arms and legs got crushed and everything went black.

When he awoke he was in the hospital, and Nurse Joy was hovering over him. 

"Oh my goodness you're awake!" She gasped, as if surprised. Marshall couldn't feel anything, his body numb. But seeing as how everything was in casts and bandages he was grateful. 

"I... I can't feel.. a-anything..." He didn't need her to explain why that was, he knew. He didn't know why she was trying to save him, he felt so cold and knew there wasn't much of a chance on surviving. "W...where's Dewott..?"

"I'm sorry sir, it didn't survive."

His heart wrenched, but he forced himself to ask another question. 

"W-what about my other pokemon...?"

"Their pokeballs are a little damaged, but they weren't harmed at all, sir can you confirm that your name is Marshall Eron? We need to contact your family." 

"T-that's...me..." His vison blanked out for a moment, for a moment he was so afraid that he wouldn't get to talk to his friends one last time, but the spike of adrenaline seemed to keep alive a little bit longer. "I-I want to see them, I-I need to say... goodbye."

"Mr Eron you're not going to di-"

"Please, please bring them in," Marshall interrupted, his begging cut off by a cough. The pink haired nurse watched him with sadness, and eventually nodded. She left the room and returned with his Pokémon, the feeling in his chest turned bittersweet. They were too well trained to flock him, rather came over slowly making soft woeful noises. 

"Hey gang... I'm.. I'm sorry.." he stared, realizing as when his chest strained that he didn't have a lot of time. "Mom and Adam.. they're going to be here soon... I.. I want you to continue with Adam okay..? Keep him safe... h-he wants to be a Pokémon master...and ... an... and just do that for me, okay? It's my finial co...command as your trainer." Marshall's breath ran out, his strength gone. His last few moments alive, he felt his Pokémon gently nudging his hands, and he knew they'd uphold his final wish.