Pokémon S17E27 - The Bonds of Evolution!

Heading towards Shalour City, Ash & Co. enter a small town where they hear that the champion of the region, Diantha, is there to officiate and take part in an Exhibition Match to begin a tournament in the town. Ash is eager to meet Diantha and challenge her to a battle, but is blocked by her staff. However, when they meet Professor Sycamore, he decides to ask for Diantha's help in researching Mega Evolution, and intends to help Ash meet her. When he does, she accepts Ash's challenge. Who will win?