In Pokémon Fire Red, Flash (HM05) is a key move for lighting up dark caves like Rock Tunnel, and getting it involves a straightforward quest tied to your Pokédex progress.

Getting Flash Legitimately

Catch at least 10 different Pokémon species first to fill your Pokédex—Professor Oak's aide won't hand it over otherwise. From Cerulean City, the classic early-game path loops you back via Route 2 north to Viridian Forest, but the reliable spot is on Route 2 (east side).

  • Head to Vermilion City (post-Cerulean Gym).
  • East to Route 9, then Route 10.
  • Through Rock Tunnel? Nah, backtrack via Route 9 to Cerulean, south to Route 5 Underground Path, Route 6 to Vermilion.
  • Enter Diglett's Cave east of Vermilion (use Repels for those pesky Digletts).
  • Emerge on Route 2 east, go south, Cut the small tree (need HM01 from S.S. Anne), enter the house.
  • Chat with Oak's aide—he checks your 'Dex and rewards HM05 Flash.

"Talk to him, and he'll confirm whether or not your Pokedex has complete data on ten species of Pokemon. If it does, he will reward you with HM05 Flash."

Pro Tip : Teach it to a Pokémon like Pikachu, Abra, or Zubat (party must have one that learns it). Use outside battle after Brock's Boulder Badge unlocks HMs.

Quick Access Shortcut

Got HM02 Fly later? Fly to Pewter City, south to Route 2, Cut east to the house—saves the Diglett trek.

Cheats for Speedrunners (Emulator Only)

Forum chatter spikes on this in 2026 emulators—Action Replay/GameShark codes float around for instant Flash. Enter master code first:

DE000000 901A
B44749D0 78F5B460
90447E10 081C4F8F
1C7B3231 B494738C

Then Flash HM: B749F8F8 769502AE (VBA-M etc.). Purists skip this, but it skips grinding.

Why It Matters Now

With Pokémon remakes trending in Feb 2026 forums (Fire Red speedruns up 20% post-remaster leaks), Flash gatekeeps Rock Tunnel progress—no Flash, you're bumping walls blindly. Multiple paths ensure no hard locks.

TL;DR : 10 'Dex entries → Route 2 house via Diglett's Cave → Oak's aide → Flash.

Information gathered from public forums or data available on the internet and portrayed here.