2023 will mark 10 years since the announcement of Gen 6 and the release of Pokemon X and Y. While looking back on the game and trying to see if the box legendaries had any ingame lore other than going to sleep for 1000 years, I ended up accidentally recontextualizing the whole ending for myself.
Here's a question you may not have thought about: Who was in Lumiose City for the parade at the end of the game?
(epilogue source - Tvoldy23 4k longplay)
On stage are Tierno, Trevor, the protagonist, Shauna, and the unchosen protagonist, as well as Professor Sycamore and Sina and Dexio, and some generic crowds as well as AZ and Floette crashing the party. Now according to the game's narration, the parade is to celebrate the five defenders of the Kalos region, and you may think that this is obviously referring to the main friend group. In this post I will be proposing an alternative theory, but first I'll go over the qualifications of each of the main five characters and their feats in the plot. Compared to SV where everyone plays some part in the final battle, XY was actually pretty lacking in its own version, but we'll see how each character contributed in their own sections.
1: The Protagonist
The whole ending sequence is all about the protagonist. You've become the new champion and caught the box legendary and personally defeated Lysandre to stop his evil plot, Sycamore personally hands you the Honour of Kalos for bravely battling Team Flare, unlike the whole friend group in SV getting marked in the Hall of Fame book, and you show AZ what it means to be a trainer again and love pokemon enough to bring Floette back. Overall the parade could pretty much just be for the protagonist and there would be no difference in the ending since the friend group doesn't even get lines. However, there are some other people who could be argued as just as worthy defenders of Kalos for joining the fight against Team Flare just as well.
2: The Other Protagonist
Out of the friend group NPCs, the opposite protagonist probably contributes the most in the conflicts against Team Flare throughout the game, actively helping you out in Multi Battles and following you for the entire Team Flare Secret HQ, so I think they deserve to be a defender too. This portion of the game is like Area Zero but you just fight generic grunts in a white room instead of bizarre paradoxes in a strange landscape.
3: Shauna
(source - MunchingOrange)
Shauna is the last member of the friend group that really contributes to defending Kalos. She joins up for the last room of the Team Flare Secret HQ despite the Other Protagonist's hesitation. Despite this she does not have any multi battles against Team Flare, and instead her contribution is opening the locked door to the legendary using a device from Clemont made for solving puzzles, which is apparently one of her main interests. Without Shauna, the Protagonist would not be able to open the door and stop Team Flare, so clearly Shauna is an integral defender of Kalos in her own way.
4: Tierno
This is where the title of "defender of Kalos" starts to get iffy. Tierno is a simple man whose goal is to make a dance team. While Calem/Serena/Shauna are deep within the HQ, the rest of the gang are on Route 10 where the stones are presumably connected to Pokemon that are being sacrificed to power the Ultimate Weapon. This is decently admirable but Tierno does not directly battle with Team Flare at all and admits that "Sina and Dexio" were the ones actually handling it, so I wouldn't exactly call him a defender but I wouldn't be opposed to putting him in the parade.
5: Trevor
Trevor has some similarities to Tierno in being that he already has a goal of completing his Pokedex and so he doesn't really get much action against Team Flare, but there is one conflict in the Frost Cavern he is involved with. Trevor fights one grunt with a Mightyena and afterwards he declares that he is scared and dislikes battling them, so I imagine he was in the same boat as Tierno in saving the pokemon and leaving the battling to the real heroes.
Sidenote: While looking into Trevor's plot relevance since I had forgotten most of it, I found some interesting information about Trevor through optional dialogue. I learned that Trevor has a sister in Lumiose City and their parents left them behind to train Pokemon. Now that's a harsh backstory.
(source)
In the postgame, Trevor can also catch a Mewtwo even after you've caught one, thanks to the power of generic dialogue.
EDIT: He also directly compares himself to AZ resorting to the ultimate weapon to resurrect Floette in this dialogue. This is pretty heavy considering Trevor's ace Pokemon is a Florges too.
"Are you wondering about the ultimate weapon, too, <player>? That man wanted to bring his Pokémon back even if it meant breaking the laws of nature. I wonder if I would feel that way if I lost my partner... This is changing the subject, but... Have you caught <Pokémon> yet?"
Also, it's hard to notice with the base 3DS resolution, but Trevor is frowning in the whole ending sequence so I don't think he really wants to be here.
So who would be the actual last two defenders of Kalos?
(source - Marriland)
(source - IGN)
Of course, it would be the masked heroes hiding in plain sight, being the only ones to use the title "defenders of Kalos" in the story, and being the only other people who are actually said to be battling Team Flare in the climax. Overall I would say that Sina and Dexio were the real defenders of Kalos on the stage in the ending of XY, but to avoid exposing their secret identities they just volunteered Trevor and Tierno to get the attention instead.