At the Santalune Gym, Viola orders a Supersonic from her Meadow patterned Vivillon, and the pink butterfly instantly flaps its wings to emanate a wave of confusion-inducing bizarre sounds. However, before the attack manages to reach Kanga, X commands a Thunderbolt and quickly dissipates it. In a sheltered corner of the room, Trevor, Tierno and Y skim through a pile of photos, although Trevor is clearly more intrigued by the battle.

Earlier, the group encountered Viola after they arrived in Santalune City and accepted the camerawoman's offer to review the pictures she took during the Vaniville incident. Upon reaching the Gym, Viola proposed a battle, and to Trevor's surprise, X accepted. Trevor has no idea if X has finally turned back into the boy who is passionate about battles, or he is simply fighting to figure out why the phenomenon known as Mega Evolution never occurred again since Vaniville. He decides that whatever the reason, it is nevertheless a good sign and feels grateful about it.

Tierno teases Trevor that he understands his delight about X being active again, but says they still have a lot of photos to review. Trevor blushes upon the remark, and quickly returns to the pictures with an embarrassed look. Indeed, the primary reason they have come to Viola's Gym was to see the photos of the Vaniville incident, which could hopefully shed some light on the truth behind its mystery. At that moment, Y stands up from her seat, and wishes to go find Shauna before it gets too late. She apologizes to Trevor and Tierno for leaving the photo task to them, but expresses her fear that Shauna might be too proud to come back, which is starting to make her worried.

Meanwhile, at the headquarters of Team Flare, an underground facility which entrance is hidden in town full of stone monuments, Aliana and Mable demand to know where Xerneas and Yveltal have gone. Xerosic replies that it is currently unknown, and Aliana laughs that it means they cannot obtain the energy needed for the Ultimate Weapon. Mable points an angry finger at Bryony to accuse her of team A's failure, but Bryony simply stays silent, and her attitude further aggravates Mable. Xerosic retorts that Aliana and Mable are in no position to pass blames, since they failed to snatch the Mega Ring containing the Key Stone despite having located it, and also failed in their attempt to steal the child of Kangaskhan which is capable of Mega Evolution. In other words, team B also completely blew the tasks assigned to them.

Mable grumbles in frustration but couldn't argue with the fact, and Aliana simply laughs it off with her usual demeanor. Xerosic reveals that the Mega Evolution mission is now being reassigned to team A, and Mable furiously demands to know whose decision it was. Bryony replies that only their boss has such authority, and Mable finds herself speechless once more. Aliana figures that team A should have already made their move, and Xerosic admits that Celosia is currently on it.

High up in the skies of Santalune, Y scouts the area in her flying suit, and Fletchy soon spots Shauna. Y quickly hovers down to intercept the girl, and feels glad to have found her before dark. She acknowledges the many thoughts Shauna probably has on her mind, but urges her to return to the others for now. To her surprise, Shauna agrees without a word of protest, and Y is somewhat astonished by her unusual obedience. She hopes Shauna simply managed to think things through, and begins to lead her to back to the Santalune Gym.

At that moment, Y notices the sword in Shauna's hand, and wonders what it is for. Shauna explains that it was obtained as a necessary tool to safeguard themselves since they cannot easily trust others, and although her answer makes complete sense, Y somehow finds it uncanny. Just then, Skitty's Pokeball falls out from Shauna's pocket, and when Y bends out to pick it up, she sees the Skitty waving to her frantically, almost as if trying to tell her something. However, before Y could reach it, Shauna scoops up the Pokeball and suggests they hurry so as not to make the others wait. Watching Shauna walk in front of her, Y couldn't help but feel that something is wrong, and hopes she is simply thinking too much.

Back at the Santalune Gym, Vivillon faints to the ground, and both Tierno and Trevor exclaim that X has won. Viola concedes that X is really strong, and says he completely walled her Supersonic, which she already considered quite indomitable. She jokes that X snatched away the shutter chance to victory she was so sure to capture, and X recalls that one of his opponents at the Junior Tournament years ago was a Noivern. Back then, he devised a strategy to handle its sound-based moves with Kanga and Li'l Kanga, and the strategy apparently proved effectively against Vivillon as well.

X wears a grin as he remembers the fond memories, and Viola exclaims that he finally smiled. X hurriedly turns away and frantically covers his face with his cap, and Viola finds it a pity that she could not capture such a great moment on her camera. She remarks that this hurts her name as the camerawoman who never lets a single smile escape her focus, and X stutters that it is just natural for him to feel elated since the strategy he came up together with his Pokemon works so effectively. X's tone then turns bitter, and he voices his surprise that Viola didn't just simply take a snapshot as she wishes, since the paparazzi seldom misses a chance to shoot and never cares about their target's feelings.

With a voice devoid of emotions, X slowly recalls what happened right after he won the Junior Tournament years ago…

Upon claiming championship, the paparazzi swarms over X and it is by luck that he manage to escape from the stage. However, their eagerness on stage, which nearly crushed him and his four childhood friends, terrified him and he tries his best to hide. He finally finds a quiet corner to take a breather, and squats down to speak with Kanga in its Pokeball, feeling glad about their successful strategy in sealing off the opponent's sound attacks. Unfortunately, he is soon discovered by two reporters, and after congratulating him with a half-hearted tone, they rudely snatch Kanga's Pokeball and force it out for a photo. X strongly protests since Kanga is already worn out, but the two men could not care less and even resort to getting Li'l Kanga out instead. They start yanking the baby Kangaskhan out from its mother's pouch, and X could only watch helplessly as his companions suffer since he does not have the physical strength to fight the men.

At that moment, and old man appears out of nowhere and hurls the two men off, knocking them out as they crash. The old man makes sure that X is alright and counsels him, urging him not to become hateful just because being with his Pokemon draws bad adults near, like the two reporters. On the contrary, he wants X to always treasure the bond he shares with his Pokemon and trust their companionship. The old man give X a ring to be worn on the wrist which has a stone embedded on it, and hopes that it would serve as a reminder of what he said…

Trevor is astonished to finally learn that X received his Mega Ring from an old man who rescued him from the two reporters who ambushed him. Yet, X says the old man didn't explain what the Ring was, nor did he reveal its purpose, which is why he was completely unaware of its powers until the Vaniville incident.

Just then, Y announces her return with Shauna, and everyone feels relieved that they managed to come back before dark. Viola offers to let them spend the night at the Gym, and Y thanks her on behalf of the group for her hospitality. Trevor giggles and thinks Shauna must be most grateful since she doesn't have to camp out again, and Shauna replies with a smile. However, the orange-hair boy seems oblivious to the flicker in Shauna's eyes which is different from usual.

Later that night, the Vaniville group rests in their rooms while Kanga and Rhyhorn settle down in the lobby of the Gym, which floor is decorated with silhouettes of bug Pokemon. In the silence of the dark, Shauna quietly slides open the door connecting the lobby and the guestrooms, and tiptoes towards Kanga. She then digs her arm into Kanga's pouch, and takes out the small rounded stone which Li'l Kanga uses to Mega Evolve.

At that moment, Y appears with Viola at the doorway and demands to know what Shauna is doing. Shauna quickly conceals her hands behind her back to play dumb, and Y questions what she is hiding. Shauna denies being in possession of anything, and Y hollers that Viola already captured everything on her camera. She angrily walks up to Shauna with the camera in hand, and confronts her about her lies. Suddenly, Shauna grabs her by the wrist, and calls her a cruel person. Given their long friendship since childhood, Shauna expresses her hurt and disappointment that Y not only doubts but also spies on her. Y argues that she only wants to find out why Shauna is acting weird, but Shauna doesn't see anything wrong about herself.

The drama soon awakes the others, and both Tierno and Trevor groggily ask what is going on. A voice in Shauna's head tells her to take action, and Shauna's face sudden turns hostile. She raises the sword that she has been carrying and starts swinging it towards Y, who is immobilized by her grasp. Just as the sword is about to make contact, Viola shields herself in front of Y and gets hit on the head. The Santalune Gymleader passes out immediately as everyone watches in horror, and Y refuses to believe what is happening in front of her eyes.

The Gym door is pushed open, and the Team Flare Scientist Celosia enters the room with a sword-and-shield-like Pokemon, complimenting Shauna for her good work. Y is furious to see that it is the red-suited people again, and demands to know what she has done to Shauna. Her words are interrupted by a Pokedex placed in front of her eyes, and she turns to see that X has also emerged from the tent and is showing her the entry of the sword-and-shield-like Pokemon, who is apparently named Aegislash and has the ability to control people and Pokemon with its spectral power.

Celosia introduces herself to the kids, and believes they should have met her comrades Aliana and Mabel. However, she hopes they realize that their battle strategies are markedly different, and she will always ensure victory for herself. With that, she takes the stone that Shauna snatched from Kanga, and both Trevor and Tierno are appalled that the woman mind-controlled Shauna to steal the item.

Celosia explains that they have obtained the group's full names and home addresses from the guestbook they signed at the Dancing Ponyta Inn, which easily leads them to find out the rest of their particulars. She knows that Shauna aspires to become a Furfrou stylist, and is also currently in search of her own Furfrou who got lost. With this knowledge in mind, it is extremely easy to make her fall under Aegislash's control, since no matter how alert she is, she will not be able to think straight when she sees the illusion of a Furfrou and a Furfrou stylist. Once she is controlled by Aegislash, everything else naturally unfolds, be it stealing the stone or even knocking out the annoying Gymleaders who gave them assistance.

In that instant, Y notices tears welling up in Shauna's eyes, and the girl, while still in a semi-trance state, softly questions if she has really done all this. Celosia is surprised that Shauna's real self is already coming back, and sweet talks her into hold on a little longer since her friends are still standing. Shauna's arms tremble as she fights the urge to raise the sword, but unfortunately, she eventually loses the battle against Aegislashs's powers and lets out a cry as she swings the sword towards her friends. Everyone tries their best to dodge while urging Shauna to stop, and after delivering another strike, Shauna simply freezes in motion and subsequently passes out.

Y hurriedly checks on her friend, and Celosia grins that the girl's body seems too frail to handle the mental stress after all. However, it no longer matters since she has already accomplished her mission by snatching the Mega Stone. X steals a glance at his Mega Ring, and feels extremely guilty that it is what caused Shauna to go through all this. Yet, Y barks that he is wrong, and retorts the culprit is not him but the people who controlled Shauna, people who resorted to all kinds of means to take everything away from them.

X realizes that Y is right, and lunges forward with Kanga and Li'l Kanga to fight. He chases Celosia and Aegislash outside, and attempts to activate his Mega Ring but to no avail once again. Trevor feels shocked since X and Li'l Kanga are already in sync with each other's emotions, and figures that the stone snatched away by enemy is really necessary for the phenomenon to occur.

X hollers that it doesn't matter since he will beat his opponent even without Mega Evolution, and at that moment, a voice compliments X's attitude, which is exactly what is expected of a Key Stone possessor. Everyone turns around in surprise to see the silhouette of a girl accompanied by a Lucario, and Trevor wonders who she is. The girl states that she is here to help, and without another word, places two fingers on the seven-coloured stone embedded in her glove, which instantly transforms Lucario into a bulkier form, with longer head appendages and a red hue at its two hands and feet…