Route 204 is located at the north of Jubilife City and south of Floaroma Town. At the middle, it is a cave, Ravaged Path. To access the top part of this Route, you must receive a badge from Oreburgh City to be able to use Rock Smash in the Ravaged Path.
Unlike the previous games Pokémon Ruby/Sapphire/Emerald/FireRed/LeafGreen, if you are caught by one of the twins' (or couples) eye, both of them will move towards you. This will be your first 2 on 2 battles using two of your Pokémon. If you only have one Pokémon, you cannot battle them.