First Pokémon Battle
When you arrive Lake Verity, you will see an old man and his grandkid. That's Professor Rowan and his kid (Dawn if you are a boy, Lucas if you are a girl). They will then exit the Lake Verity.
The professor has left his briefcase on the grass patch and your friend decided to check it out. As you are looking at the briefcase, two Starlys fly from the surroundings and attack both of you and your friends. Frantically, you decided to open the briefcase and use the Pokémon inside. There are three Pokémon. They are the Grass-type Turtwig, Fire-type Chimchar and Water-type Piplup. Choose one of them carefully because it will stay with you for the rest of the journey.
Once you choose your Pokémon, you will then battle with the wild Starly. Tap "Fight" on the tap screen of your Nintendo DS to fight it. Choose the attack and defeat the Starly. This will be your first Pokémon battle. After you defeat it, your rival will comment about the fight. If you use Turtwig, he will use Chimchar. If you choose Chimchar, he will use Piplup. If you take Piplup, he will use Turtwig. The kid earlier went back to retrieve the briefcase, and find out that your friend and you have taken the Pokémon from the briefcase. The kid take the briefcase and run away from Lake Verity. Go to Verity Lakefront and chat with the Professor Rowan. The professor will just look at the Pokémon then walk away. His kid will tell you to visit the lab in Sandgem Town. You will then return home. See Twinleaf Town to continue the story.