Ash finds a mansion that says it's a gym. After finaly getting past invisible walls and getting pined by throwing stars. He gets challenged by a pokemon trainer who has only a Venonat.
Koga apears in a cloud of smoke "Very good Ash. I see you are skilled. I only had her fight you to test your skills. We may battle" Ash was freed. In the fight Charmander demolishes his entire team. "Very good. You have earned the Fog Badge" he gives it to Ash.
When Team Rocket shows up. Koga pulls out his Haunter "I did not use all my pokemon yet" It defeats both of the Rocket Member's pokemon with night shade. (A/N Our hero Ash has obtained his 6th gym badge. Only 2 away from challenging the pokemon league.)