Stainless Steel

The boy who laid on his back on his messy king-size bed yawned, tossing a Poké Ball into the air and catching it repeatedly. His dyed-gray hair, which was naturally brown, reflected the golden light of the extravagant chandelier hanging from the high ceiling, and his steel-gray eyes gazed into space, bored. The floor of the bedroom was littered with stones from around the world: Moon Stones from the Kanto region, Sun Stones from Johto, and even a meteorite or two from around Hoenn. A small, blue, cylindrical Pokémon with a single red eye hovered curiously over to the boy.

—The opening paragraph

During the games Pokémon Ruby, Sapphire and Emerald, you meet the enigmatic Steven Stone, the son of Devon Corporation's president. Over the course of the games, you encounter Steven several times, culminating in a battle with him as Champion in Ruby and Sapphire, or as a former Champion-turned-wandering trainer deep within Meteor Falls in Emerald.

However, unlike the Champion of the original games, your rival, there is no in-game backstory detailing Steven's rise to the Championship. With Stainless Steel, Lugion (aka CaBrPi on FF.net and Mothra Freak on various kaiju forums) introduces us to a young, teenage Steven Stone, a bored, lonely rich boy wasting away in his bedroom. After a strangely convenient turn of events, Steven sets out on his own, despite his father's protests, on a quest to become the greatest Pokémon Trainer in the Hoenn Region. However, as any trainer should, Steven meets rivals and friends, and comes into conflict with the (seemingly) evil Team Millennium.

Stainless Steel is a Pokémon fanfic by "CaBrPi". You can read it here.

Tropes used in Stainless Steel include:

A Boy and His X: It's Pokémon. What do you expect?
Action Girl: Winona.
Ambiguously Gay: Wallace. Oh, so much.
Backstory: For Steven Stone.
Cool Old Guy: Captain Briney.
Extra Ore Dinary: Steven.
Five-Man Band: Steven is the hero, Wallace is the lancer, Maxie is the smart guy, Archie is the big guy, and Winona is the chick.
Large Ham: Wallace, but it's actually a part of his personality.
Two Guys and a Girl: Steven, Wallace, and Winona.