Amber

The summoning circle shone brightly as mana swirled around it, telling its spectators that the Servant was successfully summoned. A brown haired man emerged from it, kneeling into the direction of the other two occupants -and Masters- in the room. There was a short silence, as the Servant took a deep breath, adjusted his glasses, and looked up resolutely.

"Servant Rider at your service; I ask of you, are you my Master?"

His gaze bore into the redhead's, trying to find out what for a Master the young man was. Cruel? Honorable? Did he uphold the rules of chivalry in this day and age? Or was he a ruthless killer, without a care in the world?

He was so fixated on the male before him, that Rider didn't notice the petite female's exasperated sigh of utter frustration. There was a cough to his side, and the blonde spoke up.

"Cease your foolish staring, Kay. You are a terrible person if the first of your thoughts are 'should I kill him or not.' Stop being wary of every other person you meet."

His head snapped to the side in all but a millisecond.

"Arth-Artoria?!" Rider's eyes widened in shock and utter disbelief as he stared at his sister-king, not processing how she could've been there. "How are you here? Wait-" here, his analytical mind processed the given information, and he brandished his sword, not caring at the surprised sound his Master gave him. His eyes hardened.

"You should be dead. How can I know that you truly are who you are proposing, or if you are merely an impostor?"

There was another exasperated sigh, and his sister's -this person's- brow twitched in frustration.

"I am your sister. How many other people do you know that look like me?"

"Prove it." he wanted to believe it so bad, but there was decidedly something un-Artoria like in her behavior.

She stared blankly at him. "… when we were little, and I was afraid of the storm, you carved me a little old lion to make me feel better."

Riders eyes widened, as the blonde's own were clouded in memory, a simple smile adorning her face. "I never told you, but it looked more like a dog than a lion."

"Artoria…"

She smiled at him. A genuine, real smile, and he felt his eyes sting. "Long time not seen, Kay."

Alas, none of them moved, not sure what to do. The last time they saw each other, they parted on a sour note, him saying she was a hopeless fool and her telling him he was not her brother anymore.

So the minutes stretched. Both staring at each other, not moving — not daring to move. It didn't help that neither one was a very sociable person, or that he was still trying to hide his glistening eyes. For the last time he had seen his sister give a genuine smile, not a smirk or a frown or a fake, was before she drew Caliburn from the stone.

There was an exasperated huff from the side -his Master, Rider noted.

"You know, you could start by, maybe, embracing each other? Telling each other how much you missed them? Cry, laugh, scream? Any thing else besides standing there, Saber."

He focused his gaze on Artoria specifically, Rider realized, and his mind went into overwork, trying to figure out the relationship between them. So focused he was, that he didn't notice the short exchange they had. He only vaguely heard an exclamation of "Shirou!" followed by a sound he never heard his sister make.

Then his brain froze.

She was hugging him. Awkwardly, yes, but his sister was hugging him.

His sister - King Arthur - was hugging him.

He returned the hug, incredulously, noting that his cheek was wet. Looking finally down at her frame, as if it was a dream, he absentmindedly noted that Artoria was blushing.

His sister didn't blush.

King Arthur didn't blush. Nor did he hug his knights or brothers.

King Arthur didn't show affection, period.

But Artoria did. The girl did what the king did not.

Rider felt like crying at the sheer irony. That she would become human only after her death - his Master called her Saber after all, one of the Classes in the holy War.

Which still left him with the question of how they stood in relation to each other.

Ending the embrace, both siblings' stared at each other. Artoria's eyes were glistening, and the smile she wore was infectious. Rider smiled back.

His sister, finally enjoying her life.

The other Servants could get the grail for all he cared. His wish had been fulfilled.

The only thing left was the relationship to his Master, and then this puzzle was solved. So Rider had to ask, against his better judgement.

"While I am also happy- really, truly happy- I am also interested. How do you know my Master?"

"Ah…" There, the slight hesitation, the way her eyes moved to the side and her blush came back. It was all new to him; seeing Artoria behave like one of those castle maids in love-

Wait.

"Artoria?"

"Shirou is…" a slight pause, her gaze scurrying over to said Master, him nodding. "… my husband."

She closed one of her eyes, waiting for his outraged outburst for whenever she did something stupid. It surprisingly didn't come.

"Your what? I think I misheard you."

"My husband, Kay." she was surprisingly bolder now, he noted morbidly, without the aforethought reprimanding. "My husband; my sheath."

Rider looked over, flatly at his Master — brother-in-law — raising an eyebrow. "You two are married?"

Shirou smiled almost apologetically, scratching the back of his head absentmindedly. "Yeah. Since two weeks ago, actually."

Biting down the curses he had in his head, he looked back at his sister, who edged away from him, standing protectively in front of Shirou.

"Are you happy?" that was the most important thing, after all. He could skin the boy alive later, still.

She nodded, "Yes."

"Good." turning again towards Shirou, Rider threatened. "If you dare hurt even a strand of her hair, you will have hell after yourself."

To Rider's surprise, Shirou didn't shrink back, but kept his position, straightening up and glaring back at Rider. "I won't."

There was steel in him, Rider mused, before visibly loosening, smirking. "Good. I look forward to work with you, then, Master."