source.
Did Shirou become Archer, despite Rin’s best efforts and the things they’ve been through together? Where was Rin during the after-credits scene?
Don’t worry and stop panicking; they’re both fine.
Apart from his smile at the end, which confirms that Shirou fulfills his lifelong dream to be the hero he’d always wanted to be that Archer fell short of, here’s what Nasu had to say on the matter on his blog:
It’s a scene that you’ll understand if you review it again, but it was easily misunderstood so it’s cut down from the script:
Wasteland scene
“After the ED. Same scene as the initial wasteland.
Shirou walks alone. Exhausted, his feet slow to a halt.
Shirou, lowering his eyes in the face of a sandstorm, notices someone’s footprints (the place where Archer stopped walking).
Shirou takes a breath, and raises his head. His face is one of pretended resolve, but also full of hope.
Shirou resumes walking in that direction, with a firm gait.
The camera stops at Archer’s trail, and the scene ends on Shirou’s back, shrinking in the distance."
(To make this easier to understand, after Shirou leaves, you can also insert Archer watching Shirou that appeared by the footprints… but I think it’d be best if you didn’t)
He’s not wandering around aimlessly, but rather heading towards a distant point.
The scene above is mostly symbolic if Nasu’s script for it is any indication. Though you can take it literally if you want to.
So whether ufotable messed it up or if they were just saving it for the Blu Rays, one thing is clear: Shirou does not become Archer and in fact surpasses him thanks to Rin, his development in UBW, and the experiences they’ve had together. Shirou does not make a contract with Alaya: seeing what happened to Archer + realizing the flaws behind his ideals will make sure he doesn’t make the same mistakes he did. In the end, Shirou has succeeded in realizing his adopted father’s ideal, and of course, fulfilling his own dream of becoming an “ally of justice”. What a really happy ending!
But what happened to Rin after all that talk about being together with Shirou?
Don’t worry, I’m pretty sure she didn’t leave him after boldly declaring her promise to both him and Archer that she’d make sure to set Shirou’s path straight so he wouldn’t become Archer and suffer a lonely life full of regrets.
Their conversation at the end of episode 25 was basically a marriage vow, where both have declared that they would never leave the other behind no matter what. They’re practically committed to each other now, and would more likely than not be hitched already had they been a little older than they are now (in case you’re wondering, they’re at least only 20 in the epilogue).
Given what they’ve both been through together, it would make absolutely zero sense for them to leave the other behind. So Rin's probably either at home (tending to kids hopefully), at the Clocktower like she mentioned, OR if at least eight years have passed since the epilogue, then she’s most likely at Fuyuki City with Lord El Melloi II (Waver Velvet) dismantling the Holy Grail System while Shirou’s on a mission. In any case, she’s just offscreen.
Come on guys, it’s kinda like marriage: just because both parties vow to be together till death do them part, doesn’t mean they literally have to be together all the frickin’ time. They’re not attached to the hip or something like that.
Anyway, hope this clears up any misunderstandings or confusion regarding the after-credits scene. Also, Rin x Shirou FTW!!