Author's Note:

This work is based on the 'good' ending of the Unlimited Blade Works route of the visual novel and anime series, Fate/Stay Night. The name of the ending is 'Sunny Day' and can be viewed either through the visual novel, or the anime OVA animated by studio Ufotable that should be available alongside the UBW anime series. An understanding of the events of Unlimited Blade Works is the minimum requirement to fully enjoy this work. I suggest watching the anime series of UBW if the reader is unfamiliar with Fate/Stay Night at the very least, however the OVA is also very recommended. I would recommend reading the visual novel entirely first but I'm aware people may not want to put in that much effort, especially if you're just doing it to read a smutty fanfic lol.

If you do have the time though, the visual novel is better than the anime, infinitely so, and deserves your attention.

Edit: I feel like I should give some extra info, seeing as this fic kinda became more lore-based than I intended. If you haven't watched the end of UBW go do that now, 'cause what I'm about to say, and this fic, spoils it entirely.

The ending of UBW (specifically immediately after Gilgamesh is defeated by Shirou) would normally finish with Gil (who is about to kill Shirou, who has run out of mana) being consumed by the Holy Grail as it searches for a new host. Archer deals the final blow, 'causing Gil (who tried to use Shirou as an anchor to pull himself out) to fall into the hole and disappear. In my fic, this is changed. Gilgamesh ends up falling down onto his back before the reality marble fades, Archer passes away off-screen without showing up at the end, and the Holy Grail also disappears following it being destroyed by Saber. As this is based on the 'Good' ending of UBW, Sunny Day, which sees Rin reinstate her pact with Saber, who lives to see past the end of the War. I wasn't really sure how to start this fic without these changes, and I felt that it is within my means to change the ending to fit my narrative, as this is a transformative work.

Also, in the case of the romance between Shirou and Rin that happens during UBW, I feel that should be ignored entirely. Yeah, they like each other, but I wouldn't really be able to justify my ship if I paid any heed to the canon couple of the route, so please allow me this.

Chapter 1. The Final Battle and a New Beginning

"Kill me"

Gilgamesh's words were quiet, but they sliced through the stiff silence. A tinge of pain carried with them, whether from true pain or the shame of defeat is unclear. The fallen king lay on the ground, his right arm two feet away from his body after being cut off, and a deep gash running from his left shoulder to his right hip.

His eyes locked onto the mongrel standing over him, crimson eyes glazed from blood loss sharpen with rage as the kid does nothing to finish him off, leaving him defeated and ashamed. The boy no longer held any hostility towards the man. Gilgamesh would not kill himself, the shame of such a thing would be even worse than this. He had admitted his defeat at this child's hands and was now being forced to simmer in the dishonour of such a thing.

The young man stood over the king, shadows falling on his downturned face. He stared at his feet, a look of deep thought on his face as the world around him, his reality marble, began to fade back into the night sky of the mountain shrine. Shirou glanced at the blond Servant, and in that moment, he thought that the damaged and fallen hero was beautiful.

Red eyes, pained and tinged with rage, glared up at him, teeth gritted as the man attempted to push himself up with his remaining arm. Blood oozed slowly and softly over the dusty ground. Bright red soaked into the torn white shirt, into the feathery blond hair, into the pale skin; like watercolour paint, the blood seeped into everything it touched.

"Why are you hesitating mongrel!?"

The King growled, impatient. The red-haired teen had been standing there, in the fading glow of his spell, doing nothing but staring at the ground and glancing at him. "I… I can't kill you…" the boy said quietly, the words cleaving the chilled winter air.

"WHAT!? YOU CAN'T DO IT!?"

The King cried out. Shirou's words were the final nail in the coffin. "You defeated me and now you refuse to deal the final blow? Do you intend to mock me mongrel!?" The blond's eyes flared with anger and hatred, adrenaline fuelling him to try to stand. However, his arm is not enough to support him, and he fell back in the dirt, wincing in pain. Frustration and shame filled every inch of the man's body as he stares up at the stars with wet eyes, the last shreds of energy he had wasted.

Shirou's expression was troubled. Eyes again focused on the ground; brows furrowed enough to leave wrinkles. His expression softened suddenly, his inner turmoil concluding. He slowly reached his hand towards his enemy into the space between them, as he steps forward to offer the man help. "Here, let me help you up."

"Why?" the man on the ground asked, shifting to try and lean on his arm again, looking up at the boy, his fury now making way for confusion, which painted over his expression.

"You aren't evil, I can tell, you had reasons for what you tried to do. I've killed people this last two weeks with questionable methods of achieving their goals but… they may not have been truly evil… I-", the young man gulped, "I want to save everyone."

Shirou's face twisted into a smile, one that did not reach his eyes. There was something else in those golden orbs, something that gave away that the 'hero' had other reasons for his actions, less… savoury ones. Gilgamesh had assumed this child was nothing more than an ordinary fool who wanted to save people, but he was intrigued by what he saw in those eyes. This fool had got it into his head that he could save his foe.

"You want to save me?" The blond asked, beginning to relax slightly. There was no point in being so tense when this person clearly had no intent to fight anymore. The king's pride had been shattered and he had no magical energy left to kill either of them. The only thing he could do is accept his situation and see where it led. For tonight, he would put his ego aside and show magnanimity to this mongrel. If he had seen pity in the boy's eyes, he would have used the remnants of his existence to try to kill him, but this kid did not even seem to understand his own actions. He had gained the King's curiosity.

"Yeah, I want to save you…

Because that's…

What heroes do right?""

Golden eyes clouded with empty ideals, dark emotions swimming deep within them, stare at the golden king as their hands met. The servant was pulled up and the pact was completed. As if to sign it off, the command seal thought to be lost was burned back onto Shirou's hand.

"Shirou!"

Two girls called out in unison from towards the lake, running towards the temple grounds where the two men had not heard them.

"Wait!"

The Knight held out her arm to stop her Master from going any further; her sword materialising in her hand as she brought her other arm back down to ready her stance for battle. The two men did not seem to be engaged in battle, they stood near to one another, any hostility lost. Gilgamesh was injured, he was missing an arm and had a gash across his chest. Shirou seemed to be bandaging the man with the remains of his jacket. Why…? Saber's eyes narrowed at the pair before Rin gasped. "What is it, Rin?" "Those are… Command Seals? What did he do? I knew he was twisted but this!?" The dark-haired girl shouted, exasperated.

"Rin, I don't understand. What are you talking about? Command Seals?" Saber's stance staggers as she turns to look at her Master, unaccepting of what her the dark-haired girl had suggested.

"Shirou is the type of person to try to save everyone" Rin sighed, seemingly drained of energy. "Even his enemies" she states as she begins to walk towards the fool and his new servant as they notice the girls at the edge of the temple grounds. "Ah jeez!"

"I WILL NOT ACCEPT THIS"

The shock of the words ripping through the cold night's air caused Rin to jump as a silver flash leapt from behind her towards the golden king. With a flash, Excalibur shone in the dark of the night, the wind that had hidden it in previous battles dissipating.

"Wait, no! Saber!" The Tohsaka mage called out, beginning to run to her servant's side.

Gilgamesh turned to face Artoria, who lowered her body, ready to pounce, eyes sharp and fixated on the other king before her. Those same eyes dart towards the boy at the enemy's side, causing him to stumble back at their intensity. "Shirou…" The woman says with serrated words. Gilgamesh shifts slightly, causing Saber's eyes to flick back to him. "Shirou get away from him" Saber demands. "No, he's not an enemy anymore!" Shirou replies desperately. "You're not stupid enough to think he's your friend now that you've patched up his wounds are you!?" The servant barked at her ex-Master. Shirou's shoulders slumped. He knew he could not win her over. Rin catches up to the group, placing a hand on her servant's shoulder to try and calm her.

"Have you forgotten that he tried to kill you? Have you forgiven him for almost destroying Fuyuki!?" Shirou's gaze fell, unable to take Saber's glare. "I… I will make him pay for what he did. He can make up for it, it doesn't mean he has to die!" They boy replied, raising his head to meet Saber's now pained expression.

"Do you honestly believe that?"

The young man could not respond. He had no answer for her.

"We're leaving" The Knight lowered her sword, the tense air beginning to fade. "Right" was the simple answer given by the girl at her side, who looked down at the ground. The two women began to walk toward the temple gate. The boy did not call out to them. He waited until he could not hear their footsteps anymore. Then he wordlessly began to walk home, out the gate down the steps, and down the road towards the residential district. His new servant followed silently, the sound of his footsteps ringing out in the silence of the early morning, as the darkness began to allow light to seep out from beyond the horizon. Shirou's mind was blank, all that he remembered of the trip was the flickering shadows cast by the streetlights, and the crisp air causing his face to go numb.

The renewed Master and his servant arrived at the gate of the Emiya household. The boy reached into his jean pockets pulling out a key to open the gate with, suddenly conscious of the situation he found himself in. He stole a glance back at the blond king behind him, who was nonchalantly taking in his surroundings. He had not said a word since they had left the temple. Shirou was unsure if it was because the man was on edge, or if he simply had nothing to say; but he noted the servant seemed pretty relaxed. He wasn't sure whether to be on edge himself. He now had command seals to control the Servant, but he doubted that they would give him any leverage.

Shirou opened the gate and walked through towards the front door. "Um… come through" he called out towards the other person, who turned to look at the boy, following through the front door. "So, this… is a Japanese style house?" The man said softly to himself as he scanned the front hallway. He must not have seen the inside of one before. Shirou took of his shoes before setting his key on the cabinet. Gilgamesh, taking the cue, also removed his shoes, struggling a small bit due the loss of his right arm. Shirou noted that despite his ego, he could be polite if he wanted to. He could easily have claimed that Japanese customs didn't apply to him and refused to comply. Shirou figured he probably didn't feel like he was in a position to rebel, or that the man had more tact than he had given him credit for.

Shirou made his way into the living room, Gilgamesh following him in. He walked into the kitchen area, finding a first aid kit he kept in the cabinet in case he injured himself while preparing food.

"Sit down and I'll treat your wounds" the boy said to the Servant who was currently standing in the doorway looking around the room with faint curiosity. The king wordlessly sat down at the low table as Shirou sat beside him. The teen could feel crimson eyes on him as he began to undo the hasty bandages he had made earlier. Gilgamesh had downed some drink of sorts back then, claiming it would stop the bleeding for a while, and it seemed to have worked. Gilgamesh's arm, or what remained of it at least, was tough to look at. The only saving grace was the fact that he had made a clean cut when he had sliced it off, which made it easier to clean. The gash on his chest was deep but did not injure any vital organs. Shirou was immediately aware that tending to this man's condition was far beyond the use of a first aid kit but he couldn't bring a Servant to a hospital. He would have to do what he could. He began to clean the wound, applying antiseptic, and covering it back up with sterile bandages. Even though Gilgamesh winced the entire time he did nothing to stop Shirou, however his glare was almost enough to burn a hole through concrete. The boy concluded that he would probably have to find a way to make it up to the guy not just for disabling him, but also for not being gentle enough when tending to him.

Shirou put away the first aid kit, sitting back down across from the servant.

"We should discuss things" the young man started, looking up to meet the king's eyes. He immediately looked away, finding their deep red too intense.

"I'm not getting enough magical energy, but I imagine you already know that" the blond servant said, shifting slightly, probably uncomfortable as he was not used to sitting Japanese style. "It was the same with Saber, I don't really know what I can do to fix it…." the boy sighed. "I need more magical energy than a normal servant to stay active in this world, the amount you're giving me is sufficient to continue existing, but if Saber attacked us I don't think I would be able to fight her off" the King grimaced, clearly troubled at the idea of being unable to defend himself; the fact that he was even telling Shirou this showed how much it bothered him. "I don't think there's any extra source I can get for you and…" the boy glanced back up at his Servant "I don't think I trust you enough to supply you with enough magical energy to fight".

"So, you trust me enough to invite me into your house and get close enough to tend to my wounds, but you don't trust me enough to supply me with magical energy?" the King scoffed. "I know you can't fight right now, that's why you've been so compliant". The man's face darkened but he remained silent. The boy was right, even if he wanted to, he couldn't fight right now. His only choice was to go along with him or kill himself, and his renewed pride wouldn't allow the latter.

Gilgamesh sighed, lifting his face to look Shirou directly in the eyes. "I will live here, simply because I feel I have no other option at this time. It is not ideal, however…

You have given me a second chance, for what reason I don't know. I also don't know what you expect of me, but I am not a fool who would turn down a chance to observe something interesting" the king stated. He still didn't know Shirou's reasoning, so he decided to use this opportunity to observe the boy to find out.

Shirou stared deep into the man's eyes. "I see." He wasn't sure what Gilgamesh had meant about observing something, but he was glad they had come to an agreement. He wouldn't had known what to do if the king had stated he didn't want to stay here. The boy remained lost in those eyes, captivated.

"… Is there something on my face?"

Gil asked after half a minute of Shirou staring at his face. "Ah" is all that escaped the boy's mouth as his eyes widened. "S-sorry!" the young man stuttered, stumbling to get up, face burning. He didn't realise he had been gawking at the King.

"Come this way, you'd prefer a western style room, yeah?" The teen said walking to the door. "I guess so" Gil replied, leaving the matter there, moving to stand up and follow. The two walked silently towards the western style rooms, which were in a separate building in the courtyard. Shirou focused on getting there as fast as possible, his body tense and his face hot for reasons his tired brain couldn't comprehend.

The two arrived at the guesthouse. "Take whatever room you want" the boy said, unable to look at his Servant. Gilgamesh looked at the young man silently for a few seconds, pondering something, before walking to some of the rooms and looking in.

"Well then… Goodnight" The King said, surprisingly polite. "Ah, yeah, goodnight. If you need me, my bedroom is at the back of the main building…" Shirou replied looking towards the room the servant had chosen but not quite at him. Gil's eyes narrowed at the act, but he continued into his room, closing the door behind him.

Shirou, now alone in the hallway, began to walk back towards the main building across the yard. The cold early morning air reminding him how hot his cheeks were. He didn't know why he was so flustered, but he figured he'd be fine by the time he got to his bedroom. As he walked into and through the empty corridor, he became cognisant of how quiet the building was now that the Holy Grail War was over.

Saber and Rin had probably gone back to the Tohsaka mansion. Shinji was in hospital. Kuzuki-sensei, Illyasviel, and Kotomine were dead. It hit him then that he wasn't sure if they needed to die. All of them were fighting for their own reasons, as was he. He had never asked them why they were in the War properly. Maybe if they could have talked, things would have turned out different? Maybe he could have saved them too? Shirou shook his head of the overly idealistic concept. He couldn't talk to people who were already dead. At least not ones that weren't Heroic Spirits.

He opened the sliding door to his room, walking in. He lay his futon down on the floor and climbed into it. He stared up at the ceiling, any ounce of tiredness and the need for sleep in that moment had abandoned him, and he found himself unable to even close his eyes. Or perhaps he was too tired to even do that. The events of the last few hours swam around his head, but he focused on the image of his new servant. The proud and egotistical King who he had shown mercy to, who he had saved.

He wondered whether the man was truly ok with this situation, or if he was now planning the boy's murder. Shirou shuddered at the thought but understood that by allowing a person who was once his enemy into his home he had all but offered him his life on a silver platter. However, he reasoned, Archer could not use the grail to destroy Fuyuki anymore, thus even if the boy died it would not be a disaster.

As the boy continued to think he noticed that he had been focusing on the mental image of Gilgamesh at the living room table from earlier, sitting completely at odds with his surroundings. That King seemed so out of place no matter where he was. His aura seemed to separate him from the space around him. Shirou's mind moved to his features, his feathery hair, his smooth skin, his soft lips, his burning eyes. The man was beautiful.

The young man felt himself start to heat up again. But he could not stop his mind from wandering. His eyes closed as if to get a better look at his fantasy, as his mind travelled down to the other man's muscular build. He wasn't built like Berserker, but his build was one of a true hero. Shirou had admired the king's strong muscles as he had treated him but now the boy desired to know more about the servant's body.

Shirou's hand began to move under the covers, stroking his inner thigh as his face flushed red. His mind refused to leave the king's body alone, and the boy was forced to deal with the physical consequences. He roughly pulled down his trousers. He felt the tension that had been building in his groin break free of its cage. He shuddered as he wrapped his cold hand around his member. The heat of his erection almost burning his hand. He began to stroke himself up and down as he began to imagine what lay under the rest of the king's clothes. The skin of his arm and chest was soft, so he could only imagine how the untouched skin of his thighs felt. His entire body was muscular, but he couldn't imagine that a man that blessed with his appearance wouldn't have a fine ass too.

Shirou's body jolted and quaked with every move he made, despite the cold, sweat poured off his body. He began to wonder what kind of sounds a proud man like that would make in bed. Would he grit his teeth and moan deeply? Or was he the type to squeal? Just as he began to imagine filling that man with his dick, he shot his load with a muffled moan over his hand, stomach, and the underside of the covers. He lay in the result of his ecstasy, bathing in his lust, as his mind began to cool off. He didn't have time to comprehend what he had just done before he passed out from exhaustion, the room once again growing silent after the laboured breaths of the boy fading to gentle sleep.