In the beginning of the game, as in any other game, you pick the trainer you want to be (male or female) and then you speak with a bunch of characters and then suddenly you run into two random people who want to battle you. Turns out these people work for Hideyoshi. You start off with an Eevee has previously revealed and your oppenents have a Tepig and Bidoof. Knowing that you're in an unfair battle with 2vs1, Onichi appears and teams up with you to face-off against the two goons. Onichi beats the Bidoof with her Jigglypuff. Then it's your turn, you advance with your Eevee towards the oppenents Tepig and attack him with tackle. It's a OHKO.
We have now completed our first battle!
Screenshots are below: