Outside the Santalune Gym, everyone watches in shock as a girl who has her long blonde hair tied into a ponytail appears out of nowhere. After declaring that she is here to help, the girl activates the seven-coloured stone embedded in her glove, and transforms her Lucario into a much bulkier and stronger form. Trevor exclaims in bewilderment that Lucario underwent Mega Evolution just like Kanga and Li'l Kanga, and is shocked that the phenomenon also happens to other Pokemon. Without another word, the girl jumps off from the Santalune Gym's rooftop with her Lucario, and dashes towards Celosia in her Roller Skates. Celosia commands a Slash from Aegislash, but Lucario easily blocks it off with its fists, which have turned red from its transformation.

Trevor remains in astonishment that more than one species of Pokemon are capable of undergoing Mega Evolution, and mutters the words over and over to himself, oblivious that Celosia has sneaked up on him from behind. The Team Flare Scientist places her hands on the boy's shoulders, and wonders if he learnt of the term 'Mega Evolution' by overhearing from Aliana and Mabel. She understands that Trevor wishes to become a scholar someday, and says as someone who also seeks knowledge, she really looks forward to his accomplishments in the future. Trevor trembles with fright as Celosia's words echo in his ears, and gradually feels dazed and confused.

Fortunately, Y orders Fletchy to attack Celosia in that instant, and the distraction puts a stop to Celosia's hypnotic words on Trevor. Y shakes Trevor violently to snap him out of his trance, and urges him not to turn weird as well. She asks if that pony-tailed girl is a friend of foe, but Trevor states that he has no idea either. At that moment, Viola regains consciousness, and replies that the girl, named Korrina, is a friend who is also the Gymleader of Shalour City. The camerawoman covers the wound on her head with a cloth, and reveals that she was the one who asked Korrina to come. Earlier, on Route 22, before she showed herself to the group, she overheard their attempt to figure out the function of the mysterious stone embedded in X's bracelet. She remembered Korrina had an identical one of her glove, which she never really paid attention to although they have been good friends for a long time. She wagered that Korrina might be able to help them out, and thus made a call to her. Viola is glad that Korrina did show up at the end, but finds it ironic that it is the worst time possible.

Korrina disagrees with Viola, and really hopes she said she couldn't have arrived at a better time. She commands a Power-Up Punch from Lucario, but the attack fails to inflict any damage on Aegislash. Korrina realizes that she is dealing with a ghost type opponent, and Celosia confirms her suspicion. The Team Flare Scientist wonders if she should regard Korrina as an unexpected thwarter or as an extra prize, and decides that an extra prize would be more appropriate since there can be no luckier scenario than to come across another Mega Evolution user after successfully snatching Kangaskhan's stone.

Korrina feels upset that she is being treated like an easy prey, and tells X that they must show the enemy the power of Mega Evolution. She hooks her arm around the boy's endearingly, and says that must get his stone back first. She winks that after they defeat the enemy, they have lots to talk about and X should tell her all about his successor ceremony, which she has come all the way to hear. X feels completely baffled by Korrina's words, but the Shalour Gymleader seems oblivious to this and says the strategy is to have X find his chance to reclaim his stone while she distracts the enemy. Without another word, the girl dashes towards Celosia again, and X sweatdrops that the plan is so straightforward.

Korrina wiggles sideways as she roller-skates, and Tierno gasp that it is Parallel Swizzle. Y wonders what it means, and Tierno, while picking up an unconscious Shauna onto his back, explains that it is one of the many Roller Skate tricks. He then watches in amazement as Korrina closes in on Celosia with a 360, a Backflip and finally a Cosmic Flip, and feels completely floored by her technique. Korrina states that Mega Evolution users need to gear themselves up to be on par with their Pokemon who have evolved beyond evolution, and says this is her way to show her worth as Mega Lucario's trainer. With that, Mega Lucario throws another punch at Aegislash, and manages to hit it this time.

Trevor is astonished to hear the term 'Mega Lucario', and X is surprised that the move not only landed but also caused Aegislash to flinch. Moreover, he finds it odd that they are not affected by Aegislash's mind-controlling powers like Shauna was, and his query is shared by Celosia. The Team Flare Scientist uses her visor to inspect the surroundings, and realizes that the aura emanated by Lucario is shielding the kids from Aegislash's spectral powers. While Celosia has her attention on her visor, X sneaks up behind her and slowly reaches for the stone in her right hand. Unfortunately, Celosia notices it just in time and jumps out of the way, laughing at the boy's futile attempt.

However, she soon finds herself immobile, and realizes that she has been caught in some kind of gooey net. Viola grins that it is her Surskit's Sticky Web, which binds its foes even tighter with struggling. Li'l Kanga grabs the chance to snatch its stone back, and everyone cheers at their success. X roars as he places two fingers on his Mega Ring, and successfully Mega Evolves Li'l Kanga. Korrina squeals at the sight of Mega Kangaskhan standing next to Mega Lucario, and the Vaniville group is bewildered to learn that 'Mega Kangaskhan' is the formal name of Li'l Kanga's alternate form. Trevor feels thankful that they finally managed to trigger Mega Evolution again, the first time since the Vaniville incident. More importantly, X initiated the process by his own will and command this time, which no doubt lifted his spirits and also allowed the manifestation of a power so great that it's nearly unbelievable.

Lil Kanga charges towards Aegislash, and lifts it into the air before ramming it down into the ground, embedding its hilt in an inverted position. Kanga then thumps the floor to create a powerful quake, hitting Aegislash hard and putting it on the verge of fainting. Celosia grunts that it should focus on its defense, and commands it to use King's Shield, which activates its ability Stance Change and transforms it from its Blade Forme into its Shield Forme. However, Mega Lucario and Li'l Kanga double team to deliver a barrage of coordinated strikes on it, which completely amazes Y, Trevor and Tierno. Korrina grins that no amount of defense will prevent a Pokemon from fainting with this kind of attack, and gives a friendly clap on X's back, causing him to choke.

X thanks Korrina for helping him reclaim the stone, but states that he actually has no idea what a successor ceremony is. His word astonishes Korrina, and she wants to know where he obtained his Mega Ring in that case. X recaps on what happened after the Junior Tournament, and Korrina queries if it was really her grandfather who gave him the Ring. X makes a brief description on the old man who saved him, confirming it to be Korrina's grandfather, and the revelation puts a frown on the Shalour Gymleader's face.

Celosia frees herself from the web with the help of Honedge, and the Vaniville group gasps that the sword Shauna used is also a Pokemon. Li'l Kanga attempts to attack it, but Honedge moves quicker and positions its blade at the baby Kangaskhan's throat. Celosia tells Honedge to drop it, since they are apparently no match for two Mega Pokemon, and decides to retreat. She activates a pair of propellers under the boots to go airborne, and takes Aegislash and Honedge with her as she bids the young trainers goodbye. As the Team Flare Scientist flies back to the headquarters, she reflects on her defeat, and believes that her attention was distracted by the presence of another prey, a mistake which she shouldn't allow herself to commit again.

Later, inside the Santalune Gym, Lucario and Li'l Kanga have both reverted to their normal forms. Shauna slowly regains consciousness, and is greeted happily by Trevor and Tierno. Viola is grateful that Shauna came around, but Shauna, seeing the bandage on Viola's head, feels extremely guilty for what she has done and curls herself up as she trembles. Viola assures her that it was only a scratch and not really her fault, but Y scoffs that Shauna is definitely to blame for what happened. Tierno tries to pacify Y, but Y takes out 'The Five People's Pact' she wrote, and reminds everyone of the fifth point: do not leave your friends, the five of us should always stay together. Shauna sobs as she apologizes over and over again, and Y, after kneeling down next to her, agrees that Shauna should apologize for making everyone so worried. However, she blames herself for not listening to Shauna's worries as well, and a tear rolls down her face. She voices out her apology to Shauna, and the two girls throw their arms around each other as they break down and cry.

Everyone feels glad to see the two childhood friends resolve their difference, and Korrina grins that it is really nice to be young. She decides to return to Shalour City since the enemy has already been defeated, and gives a pair of Roller Skates to Tierno as a gift. Tierno immediately thanks her, and gasps that they are the special gears that can be attached to any kind of shoes. Korrina is pleasantly surprised that the big boy knows so much about them, and reveals with a giggle that she is actually a member of the Association for Promoting Roller Skates.

Korrina then notices Trevor's interest in Lucario, and remembers his astonishment when he knew that Pokemon other than Kangaskhan could Mega Evolve. She tells him that there are many Pokemon capable of Mega Evolution, and some trainers even command more than one in their team. Hearing Korrina's words, Trevor suddenly gets a vision in his head, and sees X as what people would probably called a Mega Evolution Master, capable of freely commanding numerous types of Mega Pokemon.

Trevor makes his way over to X, who is sitting cured up in a corner, and urges him to grab this rare chance and learn more about Mega Evolution from Korrina. However, Korrina firmly declines, and states that she will not recognize X, which startles both X and Trevor. Korrina remarks that she came after Viola contacted her due to her interest to meet someone who also possesses the Key Stone. Yet it turned out that X is in no way a formal successor, since Mega Evolution should be passed on in a formal successor ceremony, just like how she received her Mega Glove. She points a finger at X, and says she has no idea why her grandfather, or more accurately Teacher Gurkinn, gave him the Mega Ring, but to her, he lacks the qualities to wield it. With that, the Shalour Gymleader bids them goodbye and storms out of the Gym.

When Trevor would think back on this day many years later, he would still remember the shocking words of Korrina, but at that time, neither him nor his friends understood the meaning and importance of Mega Evolution succession…