Lucario and Korrina have known each other for a very long time since the former was a Riolu and have been very best friends. Through training, Korrina managed to evolve Riolu into a Lucario and continued being friends.
When the heroes were traveling on the road, they encountered Korrina and Lucario, who won 98 battles and decided Ash to be her next challenger. Ash agreed and had Pikachu battle Korrina, using his Pikachu. Pikachu started with Quick Attack, hitting Lucario, followed with Iron Tail. Lucario blocked the attack and used Swords Dance. Lucario used Bone Rush twice and defeated Pikachu. After the battle, Korrina and Lucario were hungry, but the heroes offered them lunch. Bonnie noticed Korrina's Key Stone and Korrina admitted she was sent by her grandfather to find a Lucarionite for her Lucario to Mega Evolve, since it was a tradition of becoming Shalour City's Gym Leader. Suddenly, Team Rocket appeared, fooled the heroes into believing Team Rocket were a bunch of psychics and took Pikachu and Lucario, wanting to take them and Mega Evolve both of them. Team Rocket fled off and took Korrina's Key Stone, off into their balloon. To free itself, Pikachu used Electro Ball, while Lucario used Power-Up Punch, redirecting the attack towards the balloon and destroying it. Pikachu tried to attack with Thunderbolt, but was hit by Inkay's Psybeam, while Lucario got hit by Pumpkaboo's Dark Pulse. The heroes arrived and Korrina had a Tag Battle with Ash. Pumpkaboo used Shadow Ball and Inkay Psybeam, but both attacks were canceled by Lucario's Bone Rush. Inkay used Tackle, but got hit by Lucario's Bone Rush and Power-Up Punch. Pikachu used Thunderbolt, blasting Team Rocket off, signalizing Korrina's 100th victory. Korrina went off to Geosenge Town and allowed the heroes to accompany her, pleased Lucario will be able to Mega Evolve soon.
During their travels with Ash and his friends, Korrina and Lucario's main goal was to find a mega stone called the Lucarionite and doing so learn to understand the importance of Mega Evolution. When they travel to the cave of trials, they encountered a Blaziken and battled it. Lucario used Power-Up Punch, but Blaziken dodged the move and hit Lucario with Blaze Kick. Blaziken repeated the attack, but was distracted by Lucario's Metal Sound. Lucario tried to hit Blaziken with Power-Up Punch, but was knocked onto the cave wall by Blaziken's Flamethrower and got bashed even further. After being encouraged by Ash, Korrina encouraged her Lucario and Lucario then fought, despite the taken damage, fiercely against Blaziken. This time, Lucario used Power-Up Punch, hitting Blaziken and was able to stop it with Bone Rush. Just as they were about to finish the battle, Korrina's grandfather, Gurkinn arrived revealing that Blaziken is his Pokémon. Gurkinn was truly impressed with Korrina's determination and felt that she and Lucario passed the test. As a reward for all their hard work, Gurkinn gave Korrina the Lucarionite so she will Mega Evolve her Lucario. Back to the starting point in Geosenge Town, Korrina pressed her Key Stone and started Lucario's Mega Evolution.
After Lucario was successfully Mega Evolved, Korrina engaged Ash and his Pikachu to a battle. Pikachu used Iron Tail to knock off Mega Lucario's Bone Rush. Pikachu used Quick Attack, dodging Mega Lucario's Power-Up Punch and hitting Mega Lucario, though he noticed Mega Lucario became angry. Mega Lucario used Power-Up Punch and while it missed, it hit Pikachu's leg without Korrina's command. Pikachu used Electro Ball, but Mega Lucario became furious and countered the attack with Power-Up Punch, then started beating Pikachu up. Korrina tried to make Lucario stop, but it kept on attacking Pikachu without listening to her commands. Just as Lucario was about to beat up Ash and Pikachu with an incredibly strong Power-Up Punch, Gurkinn sent out his own Lucario to put a stop to the rampage. After that, Lucario returned to its normal form and was taken to the Pokémon Center. After Lucario and Pikachu were healed, Gurkinn engaged his granddaughter in a battle so he can show her why her Lucario lost complete control of itself when Mega Evolved. Both Lucario Mega Evolved and used Bone Rush to battle each other with it. After getting hit by Gurkinn's Mega Lucario's Aura Sphere, Korrina's Mega Lucario lost its control again over its Mega Evolution. Korrina's Mega Lucario started disobeying Korrina and was quickly defeated by Aura Sphere. Korrina was so confused about why Lucario can't control itself when Mega Evolved, but Gurkinn tells her it is because of her lack of understanding Mega Evolution and Lucario's uncontrolled arrogance. Gurkinn furiously ordered both Lucario and Korrina to travel to the Pomace Mountain where they would train with another Mega Evolution expert named Mabel, who taught Gurkinn from when he was a young boy. Korrina obeyed her grandfather's command and Ash and his friends went with her as well.
While going to Pomace Mountain, Ash trained with Korrina. Pikachu used Thunderbolt on Lucario, who dodged and used Bone Rush, but missed as well. Pikachu used Iron Tail and Lucario Power-Up Punch. Korrina cheered for Lucario, but reminded herself she should command Lucario rather than letting it use moves on its own. As they had a meal, Korrina admitted she had Lucario since it was a Riolu and they even had a battle with a Mega Ampharos. The heroes took a path through a tunnel, but were scared off by some Noibat. Ash, Bonnie, Serena and Lucario were split from Clemont, Korrina and Pikachu. Both groups tried to search for each other, but since it was getting late, they quit and postponed the search. Lucario was worried for its mistress, while Korrina suspected when Mega Lucario was battling, it may not have even heard her commands, due to the rage consuming it. Lucario tried to train, but thinking how it may have injured Pikachu, stopped. The following day, Clemont and Korrina were ambushed by Team Rocket, so Korrina relied on Ash's Pikachu. Lucario came in time to block Meowth's Fury Swipes with Bone Rush. Since Team Rocket had their Pokémon being powered up by devices, Korrina had no other choice but to Mega Evolve Lucario, who used Bone Rush on Inkay and Pumpkaboo. Mega Lucario went angry once more and started attacking the heroes. However, it saw Korrina's Key Stone and halted its rage a bit, then started to listen Korrina. Mega Lucario used Bone Rush and defeated Team Rocket. After the battle, Mega Lucario reverted to its original form and fell on the floor from exhaustion. Korrina held its paw, assuring they will find some means to control Mega Evolution properly.
When they arrived at the Pomace Mountain, Mabel and Korrina engaged in a battle with her Mawile, which can also Mega Evolve. Mabel Mega Evolved Mawile, who dodged Mega Lucario's Power-Up Punch. Mega Lucario attempted to attack with Bone Rush, but missed and got hit by Mega Mawile's Iron Head. Mega Lucario became furious once more and attacked with Power-Up Punch, but missed and got defeated by Mega Mawile's Fairy Wind. Mabel then decides to have Korrina and Lucario help her arrange a lot of flowers with her, which Korrina accepted. But after several days of flower arranging, Korrina got so confused to why she wouldn't give her the special training like she asked Mabel to. But Mabel told her that the flower arranging was in fact the training all along. Mabel told her that flower arranging was to strengthen the bond with Lucario and Korrina and to let Korrina know that both she and Lucario have same goals, even if they view that goal from a different angle. All of a sudden, Team Rocket appeared and took Pikachu and Mawile. In rescuing the Pokémon, Korrina once again Mega Evolved her Lucario, who used Power-Up Punch, though it was countered by Inkay's Psybeam. Mega Lucario dodged Pumpkaboo's Shadow Ball, but after getting hit by Psybeam, it went berserk. Mega Lucario went to attack, but Korrina stopped Mega Lucario, who bit her arm. Following Mabel's advice, Korrina managed convince Lucario to remember what all of their training was for and both of their hearts are one. In the process, Mega Lucario, seeing the flowers it and Korrina were arranging before, finally gained control of itself and its anger ceased. Mega Lucario used Bone Rush to counter Pumpkaboo's Dark Pulse and Shadow Ball, causing Inkay to accidentally hit Pumpkaboo with Psybeam. Mega Lucario used Bone Rush on Pumpkaboo, who landed on the cage, which opened and Mawile and Pikachu were rescued. Mega Lucario earned Aura Sphere to send Team Rocket blasting off. The next day, Korrina and Lucario bid farewell to Ash and his friends and will be looking forward to their gym battle with each other sometime.
After coming to Pokémon Summer Academy, Ash informed Professor Sycamore of Korrina and her Lucario, who has the ability to Mega Evolve. This pleased Sycamore, who thought Ash would benefit of the experience of the Pokémon Summer Camp for the Gym match.
After the heroes arrived to Shalour City, they met up with Korrina and Lucario. Before going to the Gym, Ash practiced his dancing strategy with his Pokémon, which ended up in failure, causing Korrina and Lucario to be startled. During the sunset, Korrina came with the heroes to the shore, showing the water goes low-tide and revealing the path to the Tower of Mastery, where the Gym is located. During the night, Team Rocket took the secret scroll and went off, so the heroes, along with Korrina, Lucario and Gurkinn, went after them. Korrina and Lucario confronted Team Rocket, who had Inkay use Psybeam to create a gap in the floor, causing Korrina nearly to fall down. Pikachu pierced their balloon with Iron Tail, so Inkay used Psybeam, which Lucario dodged. Pumpkaboo used Shadow Ball, which was deflected by Lucario's Bone Rush. Inkay, Pumpkaboo and Meowth attempted to attack in the same time, but Korrina Mega Evolved Lucario, who did not went berserk. Mega Lucario used Bone Rush, deflecting Pumpkaboo's Shadow Ball and causing Team Rocket to blast off.
Sometime later, Korrina used her Lucario as her third and last Pokémon during the Gym Battle with Ash in its Mega Evolved form. Mega Lucario used Aura Sphere, so Fletchinder used Steel Wing to counter the attack, but was defeated by its Power-Up Punch. Ash sent Hawlucha, who used Karate Chop. Mega Lucario dodged its move, along with Flying Press and defeated Hawlucha with Aura Sphere. However, when it went up against Pikachu, the two Pokémon seemed to be evenly matched. Pikachu used Quick Attack with Electro Ball, but the move was negated by Mega Lucario's Bone Rush. Pikachu used Iron Tail, but was kicked off by Mega Lucario. Pikachu hit Mega Lucario with Thunderbolt, but Mega Lucario retaliated with Aura Sphere. Pikachu endured Mega Lucario's Metal Sound and hit it with Thunderbolt. Mega Lucario attacked with Aura Sphere, but the attack got countered by Pikachu's Iron Tail. Mega Lucario clashed with Pikachu, using Bone Rush against Iron Tail. Mega Lucario attacked with Power-Up Punch and got countered by Pikachu's Iron Tail. To finish the battle. Mega Lucario used Aura Sphere against Pikachu's Electro Ball. Pikachu, however, used Thunderbolt, hitting Mega Lucario and defeating it, causing Lucario to revert back to its original form. Ash won him his third Kalos Badge, the Rumble Badge. After the intense Gym Battle, Ash and Korrina agreed to battle again someday.
Korrina, Lucario and Gurkinn were referenced by Clemont, who remembered Ash's gym battle against her as one of his greatest battles when he decided to return to Lumiose City to train for his battle with Ash.
Lucario was seen watching the Pokémon Showcase Master Class on television with Korrina and Gurkinn. Lucario fought as Mega Lucario against Alain and his Mega Charizard when Alain challenged Korrina for a Gym Battle. However, Mega Lucario was defeated by Mega Charizard.
Korrina and her Lucario watched Lysandre's broadcast from Lumiose City.
Lysandre explained to Alain all the battles he had with trainers that wielded Mega Evolution was to collect the energy required to control Zygarde.
|Swords Dance||Mega Revelations!|
|Bone Rush +||Mega Revelations!|
|Power-Up Punch +||Mega Revelations!|
|Metal Sound +||The Cave of Trials!|
|Aura Sphere +||The Bonds of Mega Evolution!|
|+ indicates this Pokémon used this move recently.*|
- indicates this Pokémon normally can't use this move.
- ^ a b XY030: Mega Revelations!
- ^ XY031: The Cave of Trials!
- ^ XY032: The Aura Storm!
- ^ XY033: Calling from Beyond the Aura!
- ^ XY034: The Bonds of Mega Evolution!
- ^ XY039: Summer of Discovery!
- ^ XY043: Origins of Mega Evolution!
- ^ XY044: Showdown at the Shalour Gym!
- ^ XY062: The Future Is Now, Thanks to Determination!
- ^ XY112: Master Class is in Session!
- ^ XY113: Performing a Pathway to the Future!
- ^ XY123: A Diamond in the Rough!
- ^ XY132: A Towering Takeover!
- ^ XY133: Coming Apart at the Dreams!