Twinleaf Town may seem like a pretty boring place, but one day, the whole world will know that this was where you began yiour journey to become the greatest Pokémon Trainer ever.
After the opening, you'll be inside your room, watching a show called Let's Ask Prof. Rowan. After it ends, your rival (henceforth called Barry) will burst into the room. He will jabber on for a while, asking you to come to Route 201. Soon, he will leave, and you should follow suit.
Downstairs, your mom will inform you that Barry already left. She will talk for a bit, after which you're free to go outside.
Twinleaf Town has only four houses, as you will discover, with yopur one at the bottom right and your rival's at the topleft. Head over to Route 201, as he told you...but this guy will stop you, suggesting you go meet Barry in his house.Head over to Barry's house, where he will recklessly bang into you with a thud (that's routine for him) and then again rush into the house. Follow him up the steps. He'll be packing his Bag, after which he'll leave. Follow him on to Route 201.