After rescuing the Devon Researcher from the Team Magma/Aqua Grunt, you go through the woods to reach the north part of Route 104.
Explore the Route
The pokémon in the north part of the route are the same as in the south.
Go west from where you entered and talk to the boy there to get TM49 Echoed Voice. As the boy points out, you can use that TM many times. It never disappears from your inventory, so you can teach Echoed Voice to as many pokémon as you want.
North of that boy, you find three berry trees: Oran, Cheri, and Pecha.
You can go into the house here. It's the Pretty Petal flower shop. The ladies here can tell you about berries. For example, you learn that the AreaNav shows where you have planted berries, and will even show you where berries that you planted have sprouted. Talk to the little girl to get a Persim Berry. Talk to the girl near the top to get a Wailmer Pail. With this, you can water the berries that you have planted in soft soil. Just check on a berry that you planted, and if the soil is dry, you will be asked if you want to water it. Say yes, and you will automatically start watering. You can walk around while using the pail to water multiple berries at the same time.
Go northwest from the flower shop and check on the empty spots in the grass to find a hidden Poké Ball and a hidden Super Potion. There is an X Attack in the top of this area.
Go back the way you came, and go east. You will run into Lady Cindy. She has a Zigzagoon.
East of Cindy, you encounter Lass Haley. She has a Lotad and Shroomish.
Go north from Haley and walk along the bridge. You encounter Twins Gina and Mia. They challenge you to a double battle with Seedot and Lotad. The two pokémon in the top row of your list will be sent out for this battle.
North of the bridge, you find Fisherman Ivan, who has three Magikarp.
East of Ivan, you find two Oran Berry trees and a Cheri Berry tree. The person to the right of the trees gives you a Chesto Berry, so be sure to plant it!
Northwest, you find Rustboro City. But before you go in, go to the northeast and walk behind the fence. You will reach a part of Rustboro City that is blocked by the fence. At the end of the path, you find an X Defense. (Is that supposed to be a pun?)
Go back to Route 104 and enter Rustboro City from the southwest entrance.