My first Pokemon fanfic wasn't actually writing, but a comic. When I was nine/ten I filled up almost two notebooks with little stories about a Pikachu, a Charmander, and a Squirtle, aka "the PokeCrew". There was one picture a page, quality a step above stick figures, and the dialogue numbered so you knew which order to read it in. The first story "Jumpy Trouble" is five pages. In it, the PokeCrew find a jump rope, start jumping, trip, tumble down a hill, and finally land in a pond.
In my last story of my second notebook, I planned to have a story-line start when the PokeCrew find out their background friends were actually secret agents. That was also the first comic where I tried having panels instead of only one picture a page, at the same time I was looking up how to actually draw. Alas, it must have been too much work and I dropped "the PokeCrew" entirely mid-story. I never tried a comic again, and my drawing skills remain at about the same "barely above stick figures" level.
Now, for actual writing, I made my first fanfiction.net account on March 14, 2011, when I was twelve years old. I'm willing to bet I posted my first story that day, but I'm not sure which. I remember posting two stories in that time:
One is an adorably old story that was based on a bunch of little Pokemon figures by brothers and I played with. I started that a bit before I posted, as I have a few pages handwritten in a journal. As I wrote, "I am doing a story with my pokemon. In my story, the world, which has no people, only pokemon, is ruled by evil Lord Rayquaza." Apparently, Rayquaza used to be a noble king, but one day he left on a journey and came back "cruel and evil, and his mind was set world domination." Upon his return, he waged a war that killed many people and made literally everyone else a slave.
In my journal, I have three pages of the story where my main character Grovyle and his friend are escaping from "slave hunters." Then I stop. For ff.net I wrote a prologue which I deleted off the site and then lost. I remember it was from the POV of a Sceptile character (who in a plot twist would be revealed to Grovyle's dad don't tell anyone). I write his arm getting ripped off because the toy Sceptile I had was broken.
The other story I posted was my first attempt at writing my current project, SoH. I actually got a review for that one. Like with the previous, I took SoH attempt 1 down and don't have it anymore, sadly (about not having it - thank god it's not floating around on the internet). I remember it well enough. I wrote a prologue and the first chapter, and there are some lines I remember in particular that are just aaahhh.