In "Pok?mon FireRed" players can get the move Flash, or HM05, from Professor Oak's assistant. They can find the assistant in a house on Route 2.Know More
The player must beat the gym leader in Vermilion City to reach this previously inaccessible portion of Route 2. From Route 11 enter Diglett's cave. Go through the cave, then head north, cutting down any trees blocking the way, and find the house with a tree blocking the entrance. Professor Oak's assistant is inside this house. When the player enters the house, Professor Oak's assistant will be located just inside. To receive Flash the player must have captured at least ten different species of Pok?mon.