Korrina steps in when Celosia attacks X, Y, Trevor, and Tierno. She and her Lucario team up with X, Garu, and Kogaru to defeat Celosia's Aegislash and free Shauna. Afterwards, Korrina refuses to accept X as a user of Mega Evolution.
Korrina leaves the group and goes to confront her grandfather, Gurkinn, at the Tower of Mastery, demanding to know why he gave X a Mega Ring. Essentia interrupts their conversation, dividing them so that Korrina is stuck fighting while Essentia questions Gurkinn about Mega Evolution. Essentia's Trevenant encases the Tower of Mastery with its roots, forcing Korrina and Gurkinn to destroy it to protect its secrets. Afterwards, Korrina helps Gurkinn walk away and hears him say that with the tower went the secrets of an undisclosed Pokémon.
Korrina is brave enough to save X and the others from Celosia, but she can also be harsh, seen when she refuses to accept X as a Mega Evolution user. She is also rather hotheaded, as she rushes to argue with her grandfather about X's Mega Ring and to fight Essentia.
Lucario can Mega Evolve, suggesting he has a strong bond with Korrina. Lucario fought Essentia's Trevenant and later helped destroy the Tower of Mastery.