Traveling back to Ylisstol, Chrom and Lissa met up with Emmeryn as Y/N met up with the Sheikah elder, Impa. He told her of his recent endeavor, how he conquered Vah Medoh and re-encountered the Rito Champion, Revali. 

Impa: Now that you have seen some of your memories, you must have started to remember certain things... Here. I will hand this over to you now, before I forget.

Y/N could see that Impa had picked up a specific garment to her side, along with a singular leather arm guard with black fingerless gloves. She then handed it towards him, Y/N holding it as he eyed it's design.

The tunic was colored a royal blue, Y/N remembering this garment from his memory. On the front of the blue tunic was a design of the hand guard from the sword on his back from the memory, the sword pointed downwards. 

In Hyrule, the garment could only be worn by those who have earned the respect of Hyrule's royal family. This was the specially made garment that Y/N wore when he was in service of Princess Zelda. The Champion's Tunic.

Impa: This is something of yours that I have been safe keeping, by request of the princess. This clothing was specially made for you when you became a Champion. Please handle it with care. 

Y/N nodded in reply. Heading into the another room, he went to try it on. Discarding his current tunic, he slipped on the Champion's Tunic, putting on the leather arm guard onto his right forearm and putting on his fingerless gloves. The tunic felt comfortable. As soon as he put it on, it felt just right. It shouldn't have come as a surprise. He wore this thousands of years ago, and when he was put into the healing chamber, his body hadn't changed one bit. Nor had he aged a single bit. He still looked to be eighteen or nineteen.

(A/N): In actual Zelda canon, both Link and Zelda are biologically seventeen. I had to change the ages a bit so I could match the ages of the other characters, whom are roughly late teens or early twenties. However, the exceptions are those with the manaketes and taguels as they age differently. Hell, Tiki in Awakening looks to be she's in her early twenties, when in actual reality, she's thousands of years old, probably older. 

Once changed, he stepped out. Impa got a good look at him, her simply smiling. She still remembered her days in Hyrule, how Y/N wore the outfit almost everyday.

She then frowns.

Impa: You may not remember your last meeting with Ganon, but it did not end well for you. If you want a different outcome this time, you'll need to be properly equipped. 

Y/N: (nod) I won't fail.

Impa: Princess Zelda is fighting Calamity Ganon all alone. You are the only one who can save her. Now go. You must!

Y/N nodded once again as he exits the room. Not even a single rest since getting back, the Shepherds were once again called out. 

The report was, a group of Plegian soldiers were sighted just southwest of Ylisse's borders. They had attacked a village in Themis and abducted the duke's daughter. The duke's daughter was also a member of the Shepherds, Maribelle. 

However, a part of the report also didn't make sense. It was said that Maribelle had invaded the country of Plegia, now demanding reparations. Of course, the Ylissean royals were not to believe the Mad King, Gangrel. Chrom wished to take them down quickly, but Emmeryn had thought to take this peacefully. They didn't want to do a war with Gangrel, so Emmeryn had offered to parley.

Despite the protests from Chrom, Lissa, and Phila, Emmeryn chose to march onward to the border.

So leaving at night, they departed for the southwest border of Ylisse, crossing through the western mountains to get to Plegia's border. As the group left the castle's walls, they were now out in the open plains. Just before they departed far from Ylisse's walls, Y/N spotted a square of some sorts.

He distanced himself from the group, making them confused as to where he was going. The center area was elevated slightly, it surrounded by a small water moat. Y/N took his Sheikah Slate off his waist and went to his album of pictures. The picture he was on matched the very same square he was on, albeit the background of the picture was different as it was taken in a different time period. He eyed the area for a bit before he gasped.

Flashback

In the center of the square were two people. Y/N was kneeling in front of a blonde Hylian girl, the blonde having her palm extended out towards him.

Behind her were others. One of them was a red Zora female, a Goron, and a Gerudo woman. Revali and Marth were among them, along with a blue-haired woman at Marth's side and a green-haired girl, who seemed to be a young girl.

Blonde Hylian: Hero of Hyrule, chosen by the sword that seals the darkness... You have shown unflinching bravery and skill in the face of darkness and adversity. And have proven yourself worthy of the blessings of the Goddess Hylia. Whether skyward bound, adrift in time, or steeped in the glowing embers of twilight... The sacred blade is forever bound to the soul of the Hero. We pray for your protection...and we hope that--that the two of you will grow stronger, together, as one.

The woman stopped and took a deep breath. The woman was none other than princess Zelda, who's gaze was casted on Y/N. Her gaze showed hints of frustration, and bits of anger.

She then continued on.

The Goron of the group rubbed his white beard for a bit before he scratched the top of his head.

Goron: Gee, this is uplifting... She's making it sound like we already lost. 

Revali: Wasn't this your idea? You're the one who wanted to designate the appointed knight with all the ceremonial pomp, grandeur, and nonsense we could muster! And might I remind you we've done this before, right after the ceremony in Hyrule when we were bestowed these outfits? And it's like I've said before, the whole thing is overkill. I'm on the same page as the princess regarding...this boy.

Gerudo: Oh, give it a rest. That boy is a living reminder of her own failures. Well, at least that's how the princess sees him.

Marth: Is there any particular reason why? Before you all came here, it seemed they got along well for the most part.

Gerudo: (sigh) It's a bit...complicated.

The group return their gaze back to the two. Zelda stopped her praying and looked down at him. Every time she looked up, she would always see that sword on her back, and yet, she could never unlock her own power.

Y/N's hair was moving with the way of the wind, him keeping his head down, bowing in respect. It's not that she hated him. She just hated how he was easily able to unlock the sword before she could manifest her sacred power.

Flashback End

Y/N opened his eyes once more, now having remembered the memory fully. While he did remember the memory, he himself couldn't remember the exact reason why Zelda had looked at him with those eyes.

He was snapped out of his thoughts when Chrom called out to him. Tucking the Sheikah Slate back onto his waist, he runs back to join the others.

Morning, Plegian Border

Now at morning, Chrom and his Shepherds, with Emmeryn, arrived at the Plegian Border. Just across it, standing on a rock with a woman, who is his right hand woman, was the Mad King Gangrel himself.

Gangrel: What's this, then? The exalt herself, in all her radiance? I fear I must shield my eyes! (laughs mockingly)

Emmeryn: King Gangrel, I've come for the truth of this unfortunate incident between us. 

???: (giggle) The truth? I can give you the truth.

Emmeryn: (furrows brow) Perhaps milady might first share her name? 

Aversa: (bows) You may call me Aversa. 

Emmeryn: Very well, Aversa. Is Maribelle unharmed?

Gangrel: Who? Oh yes, the little blonde brat. 

Gangrel motions for someone to step forward. From behind Plegia's border, a brigand from Gangrel's army comes forward, along with a Maribelle, who was struggling to get free as her hands were bound together and the brigand was holding onto her tightly.

Maribelle: Unhand me, you gutter-born troglodyte!

Lissa: Maribelle!

Maribelle: Lissa? Darling, is that you? 

Aversa: The girl crossed the Plegian border without consent. And what's more... She wounded the brave Plegian soldiers who sought only to escort her safely home.

Maribelle: Lies! You speak nothing but lies, hag! Did they not teach the meaning of the word "truth" in wretched-crone school!?

Y/N narrowed his eye in suspicion. From what he could see, Maribelle wore the clothes of a troubadour, a person who rides into battle atop horseback with staves, which are used to heal allies. In terms of offensive capabilities, Maribelle seemed to lack any of those unless she knew magic. Other than that, she knew nothing about how to use any weapons.

Aversa: (grin) You see? No manners, at all. Such a nasty little bird simply had to be caged. 

Gangrel: Such a violent temper speaks to her guilt. This will call for a weighty punishment. And if she were to later confess being an Ylissean spy? My goodness! It would take an act of considerable good faith to repair our relations. 

Maribelle: I have done nothing wrong! It is they who should confess! They are the ones who invaded Ylisse. They razed an entire village! When I attempted to intervene, they took me and dragged me across the border! Let the plundered shops and charred homes of that village serve as my proof!

Gangrel: That would only prove that Ylisse has a bandit problem--something I hear oft of late... But indeed, tonight I shall weep salty tears into my pillow for your dead villagers. 

Maribelle: Your Grace, please!

Emmeryn: Peace, Maribelle. I believe you. King Gangrel, I request that you release this woman at once. Surely you and I can sort out these affairs without the need for hostages. 

Gangrel: Without so much as an apology? Why should I even bother with parley? I'm within my rights to have her head this instant and be home in time for supper.

Chrom: You black-hearted devil!

Gangrel: (shakes head in disapproval) Control your dog, my dear, before he gets someone hurt. 

Chrom stood down, growling in anger. Should he make any wrong step, it could cost Maribelle's life.

Gangrel: (clears throat) Now then, your Graceliness. Perhaps we can arrange a trade? You give me the Fire Emblem, and I return Mari Contrary here in one piece. 

Emmeryn: You would ask for Ylisse's royal treasure? But why?

Gangrel: Because I know the legend! The Fire Emblem is the key to having all one's wishes realized. I have desired it for years. Years! Yet, my birthday comes and goes each year, and nothing from Ylisse. Heheh...

Emmeryn: The Fire Emblem's power is meant for a single purpose, King Gangrel: to save the world and it's people at their hour of most desperate need. Would you claim a more noble wish? 

Gangrel: I want what every Plegian wants--a grisly end for every last Ylissean! What could be more noble than that? 

Emmeryn: What?

Gangrel: Surely you have not forgotten what the last exalt did to my people? Your father named us heathens! His "crusade" across Plegia butchered countless of my subjects and my kin!

Emmeryn: ...I have never denied Ylisse's past wrongdoings. But I have sworn to never repeat those mistakes. Ours is now a realm of peace. 

Gangrel: Yours is now a haven of hypocrisy! Now give me the Fire Emblem!

Maribelle: No, Your Grace! I'd sooner die than act as a bargaining chip for this filthy reprobate!

Emmeryn: No, Maribelle...

Gangrel: (groans) Ugh... Taaaaalk talk-talk-talk-talk. It's time to speak louder than words! This negotiation is over, Your Luimosity! I shall have the Emblem if I have to pry it from your shiny dead hands!

More of Plegia's brigands step forward, Maribelle now being taken back behind the border's lines. In response to the oncoming fight, Chrom drew Falchion from it's sheathe, Y/N doing the same with his broadsword off his back, taking his shield as he raises it up.

But Chrom attacked first, slaying the first Plegian brigand as it falls onto it's back, dead. Blood began to seep out from his wound, creating a puddle underneath him. Chrom then points Falchion towards Gangrel.

Chrom: Stay back! Or you'll all suffer the same fate!

Gangrel: Now that's a declaration of war if I've ever heard one... A big, messy war that will bleed you Ylisseans dry!

He then begins to laugh manically, ordering more of his troops to get ready for battle. Just then, wind magic surrounds the brigand that held Maribelle, the wind magic cutting from all different angles as he falls over. Chrom and his Shepherds look to see it was one of their very own Shepherds, Ricken, a boy who was not supposed to be there.

Having freed Maribelle, the two took off in the direction of Chrom's army. The war between Ylisse and Plegia have now started because of this altercation.

Robin began to give instructions, the white-haired girl instructing Y/N to go on over to help the two that were coming over. Nodding in reply, he took off.

He darted up the rolling hills, Plegia's army having been posted up on the high ground. The commander was at the top of the hill, overseeing the battle as he rode atop a wyvern. But right now, that wasn't his main concern. His main concern was to get Ricken and Maribelle over to the rest of Chrom's army.

Climbing up the first hill and reaching the top, he side stepped, dodging an attack from a brigand's axe. Taking his sword, Y/N brought it behind him, him charging up his attack as he spun in a circle, doing a spin attack. He spun multiple times, cutting and slicing up multiple brigands as more came down the hill to stop him. Blood flew in the air, some getting on his shield and sword.

Although he disliked bloodshed, Y/N had to do what he must do. Right now, it was war. His life was on the line. In order to save his own life and his allies, he must take the lives of his enemies.

Two enemy mages posted themselves at the top of the second hill, readying their magic as the took out their tomes. But Y/N was quicker, quickly putting his sword and shield away as he drew his bow and two arrows from his quiver that hung from the back of his waist. Drawing them both back on the bowstring, as far as he could, he lets them go, the arrows flying.

Curving through the air, the two individual arrows strike their individual targets in their heads. The two mages then drop dead onto the ground, Y/N continuing his ascent. 

Y/N joins the two Shepherds he was asked to escort up onto the slope leading to the second hill. Just before they could move, they heard an angered yell, a brigand heading straight for them. Ricken prepared to cast his magic, but Y/N quickly got in the way, raising his shield up for defense as the brigand swung his blade. The blade bounced off of Y/N's shield, creating small sparks as it struck the metal. Now, it was Y/N's time to counterattack. Y/N went in for a shield bash, hitting the brigand's face with the end of his shield, then following up with a sword thrust, the attack piercing the brigand's chest, right through his heart.

The brigand coughed up blood, Y/N taking his sword out of his chest as he uses his foot to kick him off. Y/N flicked the blood that was on his blade. He was then drawn to his right, seeing a mage casting magic at him. Just before the mage was about to release his magic, wind magic appeared all around him, damaging him and eliminating him. Y/N turned to the caster of the magic to see it was Ricken, who nodded at him with a smile. Y/N nodded back and turned to the rest of the battlefield.

The rest of the Shepherds were slowly progressing up the hill, heading straight for the commander, who seemed to be nervous and sweating. Both Chrom and Robin were paired up together, the two heading up the hill as quick as they could to get towards the commander. Some of the commander's soldiers were beginning to flee, it looking like the commander was beginning to flee himself.

It was at this time, Y/N wanted to test out his new ability he got from Revali. He never really got to try it out since defeating the Divine Beast, so now was the best time.

The Hylian warrior crouched down, taking a deep breath. The two Shepherds look at him confused, wondering what he was doing. As soon as Y/N exhaled, a torrent of wind surrounded him, an updraft from below pushing him upwards as he took out his paraglider. Y/N could also see that a ghostly image of Revali flew around him.

Once more drawing his bow with an arrow, time seemed to have slowed down as he began to focus. His aim was pinpoint on the enemy commander. 

Letting go of his arrow, his arrow flew, darting through the air at high speeds. The arrow struck the wyvern the enemy commander rode upon, the winged beast letting out a pained groan as it fell onto the ground, dead. The enemy commander was flung off, tumbling down the slope and onto the second hill.

The battle was now over. As soon as the enemy commander had gotten up, Chrom and Robin were swift to cut him down.

Soon after the battle, Y/N joined up with Fredrick, the two heading back to Chrom, Robin, and Emmeryn.

Chrom: Forgive me, Emm. I acted rashly.

Emmeryn: It's all right, Chrom. King Gangrel is the one at fault here. You were only protecting me. 

Y/N: If I may. The Plegian king will begin about rallying his forces, if they are not mobilized. 

Fredrick: He is right, milord, milady. I suggest we make haste back to Ylisstol and discuss our strategy. 

Emmeryn: Of course, Fredrick. It seems war is upon us. We must protect the Ylissean people at all costs. 

With their problem ended, a new one had arisen. The Shepherds began to head back towards the Ylissean capitol as fast as they could. War is upon them, and many lives would be lost should it be prolonged much longer.