Team Summer, the secret force behind crime-fighting in Xandau, has lost their leader. As they scramble for a new one, the opposing Team Winter has started to move out, hoping to take over the region of Xandau for themselves. Meanwhile, 10-year-old twins Anastasia and Alexei Saffron are about to take their first step on their Pokémon journey. Leaving the comforts of Aventurine Town behind to explore Xandau, and excited to start fulfilling their dreams, they are unaware of the tension about to explode right beneath their feet.