This short story is a collaboration with a friend of mine over on Reddit. He drew the picture at the bottom and came up with the idea of Long Rin.

I'm Sorry Shirou


10th Day: Einzbern Forest - Tohsaka Sacrifice
Illya is safe.
The shadow disappeared.
When I look up from the ground, I see why nothing hit me despite my attempt to shield Illya with my own body. Someone else did the same for me.
In front of me lies a jumbled mess of body parts that used to be Tohsaka and her Archer. I can't really tell where the blood starts and their clothes end.
Everything is just red and wet and I quickly turn to retch.
"Shirou?"
Oh no. Not Illya. I can't have her see this. But as I turn around to press her onto the ground and force her eyes away, she's already staring at the gore.
Still, I try to pull her away, but she persists. While I feel weak and fragile, she stands there with a sort of sorrowful finality.
She's taking in the scene and there's nothing anyone - much less a failed hero of justice - can do.
Failed.
I failed.
Shirou Emiya failed to protect someone close to him, yet again.
Except this time it wasn't 'just' a Servant but a real life, flesh and blood, human being.
This is my ultimate fail-
A blue light explodes into being just above the chaos of limbs. Glowing tendrils stretch out towards Tohsaka and Archer and I just can't take it anymore. Whatever this is, I am going to stop it. I dash towards it.
"You will not defile their corpses!"
Something is already happening while I close in on them. The light is probing them, analyzing them.
"Leave them b-!"
I fully intend to throw myself on top of the mess - if only to stop the light from doing whatever it is doing. Just before I reach them however, their flesh starts moving.
A small hand touches mine as I stare in horror.
"It can't fix them. Parts of them are gone. Erased."
What do you mean Illya? How do you erase physical things?
I can't bring myself to ask, so I stay silent instead.
"It doesn't realize. Or maybe it's in denial. Or... or could this be desperation?"
Illya's voice goes from pity to confusion, only to end up with blank horror.
Her hand clamps down harder on mine and the pain feels like a reasonable start for the punishment I deserve for letting this happen.
In front of me, the light has finished assembling Tohsaka and blinks out of existence. Except it didn't quite know what to do with the extra parts. I count two pairs of elbows. There is probably one hip too many in there. And that only emphasizes the fact that Archer's legs are far too long for Tohsaka's upper body.
The eldritch abomination in front of me has a look on her face that is a mix of confusion and migraine. Yet, it manages to speak using Tohsaka's voice with no regard for the life that was lost.
"I... I have to stop that shadow."
Then, she's off.
With the speed of a Servant, she pushes off the ground and dashes away. What do I do now? Is the shadow gone for good? No. Wait. I need to slow down. Think.
I need to take care of Illya first and foremost.
"That is an unexpected development."
I wheel around towards the voice, ready to defend Illya from whatever new enemy just appeared.
"Rider?"
"Sakura sent me to keep you safe."
"Ah."
Well, this is awkward. I still don't know how to behave around Rider.
Something tugs on my hand. Right. Illya.
"Shirou. We should go. We need to sort this out."
"Yeah, Illya, about that. What just happened with Tohsaka? Is she... She was still moving, so...?"
Illya looks to the ground. I won't be getting any good news from her.
"I agree with the Einzbern Master. We should leave to get you to safety."
Great. Why is everyone concerned with keeping me safe when I'm the guy in the group? I'm the one that should be protecting them. How can I ever become a hero of justice if I'm unable to save Saber and Tohsaka and now have to be taken care of by Rider and a little girl?
"Right. I'll take you somewhere safe, Illya."
I start walking through the forest towards the city. If I remember correctly, this way should lead out of here and home where I can protect Illya better and figure out what to do next.
"I'm sorry, Shirou."
I don't even have the strength to tell her that no - she isn't the one that should be sorry. This is all on me.


10th Day: Church - Artificial Counter Guardian
After exiting the forest, Illya drags me towards Shinto and the church instead of letting me go home. She wants to figure something out and Rider agrees, so I go with them too busy with my own thoughts to question them. Father Kotomine is Tohsaka's guardian and so it's probably for the best to straight up tell him what happened.
The city glides past me without leaving much of an impression. When we enter the church, another person is already present. I'm not sure how to approach the subject with this stranger around and I am painfully aware of how Rider's choice of dress could be frowned upon in a place like this.
"Uhm. Father Kotomine. It's about Tohsaka."
He shows no reaction, his face set in stone. I can't help but look at the stranger again in the hopes that the father will take a hint and send him away.
Oh no. The stranger is staring down Rider. I knew she was going to attract attention. Slowly, I shuffle over to stand in front of her.
"I must say, I did not expect you to show up with the Einzbern girl and the Servant of the Matou."
Alright. So the father is just going to go ahead and talk openly about the Holy Grail War in front of the foreign looking stranger.
Wait. Foreign looking?
"Is he a Servant?"
This manages to cause a smile from the priest. To think that he reacts stronger to this question than to a grave announcement involving his charge deepens my feelings of revulsion towards the man.
"Something of the sort. Now, what did you have to tell me about Rin?"
The man is infuriating. First, I get no reaction about Tohsaka and now that I try to figure out what's going on with the stranger, he switches the topic back to her. Again without showing the least bit of concern for her. It's infuriating.
"Rin Tohsaka and her Servant were killed by a black shadow."
I didn't expect Illya to go ahead and straight up tell him what happened.
"The Counter Force showed up and did something to their bodies and now its creation is running around looking for the shadow. But it won't find it yet. The shadow has retreated for now, although it'll have to come out again to feed, soon."
Wh-what? How does Illya know all these things?
"Hold on a second. What's a Counter Force?"
Am I the only one that doesn't understand?
There's that grin again. I ball my fists and try to stay calm. If only I knew more about all of this or had enough power to do something.
"The Counter Force is a sort of failsafe mechanism that protects humanity. Very interesting indeed."
He shouldn't be looking so smug.
"Well it took Tohsaka's corpse and turned it into an abomination. Don't you care about that? That's not interesting, it's horrible! You're her guardian, act like it."
While I go on a rant, the blond stranger gets up to stretch.
"Technically, he's not her guardian anymore. Whatever may be the case, it looks like I won't have to sully my blades with the blood of that miserable thing after all."
He walks off towards the back of the church under Rider's watchful eyes.
"Let's go, Shirou."
Illya is tugging on my hand.
"I just wanted to let that priest know that there'll be someone new to clean up after and that they'll most likely be very messy. Now that we've told him what we needed to, we should go home and strategize."
"Eh~? You just want to go home now?"
She's already dragging me along. I look back at father Kotomine one last time, noting the eagerness that he isn't even trying to hide, before turning back around. This man isn't my priority right now. I swore to keep Sakura safe which means that I should go and check up on her soon.


Intermission: Long Rin
They were broken at discovery.
Scrambled eggs.
Someone has added too many spices and now it's all wrong.
Loss of personality during fusion is compensated with a new proto-personality.
A single thought is birthed into emptiness.
Destroy the shadow.
Warrior of Justice.
Guardian.
Agent of Alaya.
The directive is implanted with force.
Kill. Protect. Kill. Kill.
Kill kill kill kill kill kill kill.
From eternal repetition breaks a memory and is immediately drowned again.
Deep slumber is less painful.
It bursts through the night on the hunt, ready to slay the shadow that threatens to devour mankind. Body working like a well-oiled machine despite the mismatch.
Two lives were lost, but something new was born from them by an inhuman entity that couldn't quite grasp the finer details of what it means to create a true human. The epitome of a Counter Guardian starts its search for a shadow that has already faded into obscurity again and won't come out to feed again for several hours.


10th Day: Dinner - Hollow Conversation
Sakura takes in the new addition to our household shyly, but I'm sure she'll come around eventually. After all, Illya isn't an active master anymore, so she doesn't pose a threat to her.
Breaking the news about Tohsaka to her feels impossible and so I'm relieved when Illya takes that task upon her. I'm not surprised when Sakura excuses herself. Tohsaka may have threatened her life, but hearing about her sudden death must have come as a shock.
As soon as she leaves, Illya turns towards me before I can go after her.
"Shirou."
"Huh?"
Why does she look so serious again? Can't we just take a short break from all of this before we have to go out and fight that shadow again?
"There's something... You said you wanted to protect Sakura, no matter what, right?"
"Yes. Father Kotomine said it will be very dangerous, even for those around her, but I decided to win the grail to fix her. No matter what."
She looks uncomfortable.
"Hey, you can get out whenever you want to. I know the Holy Grail War is scary, especially for a girl as young as you."
Illya shakes her head at that.
"It's not that. It's just..."
She scrutinizes me and whatever she finds, it sets her mind.
"Never mind."
I'm not sure if Illya will be alright, but there's nothing I can do about it at the moment and so I get up, give her head a quick pat, and walk over to the kitchen.
"Want to help me make some nice dinner to cheer up Sakura?"
At first, Illya gives me a defeated look, but then she smiles and jumps up.
"Yes! I've always wanted to do something like learning how to cook from my big brother!"
While cooking, Illya bounces around me, causing about as much trouble as her help is worth, but the feeling of wholesomeness that is slowly returning makes up for that. Maybe, if Sakura comes back to a steaming pile of freshly cooked food, she'll cheer up a little as well.
Still, Tohsaka's death aches and keeping busy by cooking doesn't quite fill the hole that she left.
By the time we start setting the table, Sakura returns and silently helps out. Even Rider joins in for the meal and so we sit around the table as four while I still feel a deep loneliness.
The conversations are hollow and I keep wondering how everybody would be doing if Tohsaka was here in my stead.
But I committed to keeping Sakura safe and so trading my life for Tohsaka's would have broken that promise. Maybe this is for the better.


10th Day: Night - Chasing After Her
"Shirou."
I've heard this name spoken by this tiny voice so many times today.
"Shirou, you need to wake up."
Wait, Illya, I have to save Tohsaka first. If I don't she'll turn into a monster and if you're also here then, then... then I won't be able to save you both and you'll doom her and I'll be a failure and-
"Shirou."
Small hands are shaking me as I open my eyes.
"Illya."
Illya?
"Wha~ What are you doing in my bedroom?"
And so close to my bed. With her hands on my shoulder. So soft and small. I shake my head.
"It's about Sakura. She's... she's sleepwalking. I think we should follow her to make sure she's alright."
Illya is lying about something but I don't care. If Sakura is out and about at night, I'll have to find and stop her. What if she runs into that shadow and is killed like all the others?
I jump up and get dressed, suddenly much less conscious about Illya's presence. The only thing on my mind now is Sakura.
If I let her die as well, I'll have given up my dream for nothing. I'll have strayed from the path as a hero of justice only to fail utterly at my new goal.
When I rush out of my room and towards the front door, I notice that Illya is following me.
"You should go back to bed. It's not safe."
She's giving me a look of disbelief.
"Shirou, I'm a better mage than you."
I- I don't have any arguments for that and any second I waste here is a second in which the shadow can find and murder Sakura.
"Fine. Let's go."
I reach for the door, when:
"Shirou."
Great. Now Rider is up as well.
"What is it, Rider?"
"I'll come with you. You don't have Saber anymore."
Fine, whatever. I just nod and leave with the two women behind me. Since I don't know where to go, I just start running. Soon, Rider takes the lead instead.
"I can feel her. Follow me."
I have a hard time keeping up with the Servant because I decide to carry Illya to speed things up and by the time we reach the inner city, I have troubles controlling my breath while my lungs are struggling to keep my body going. At least Illya is doing fine.
"She was here. It's just a little further."
I nod again and we follow Rider out towards a park. This time, we move a bit more slowly and stealthily, so I set Illya down to walk the rest of the way herself.
There. I see something standing between the trees. Is it Sakura? The height seems about right and- are those people lying on the ground?
Before I can make out what exactly I'm looking at through the darkness, a bright light illuminates the scene. A glaring red arrow hits the ground only inches away from Sakura who is covered in blood.
Shit. So someone got to her already. Someone hurt Sakura. And now someone is shooting arrows at her.
"SAKURA!"
I break into a sprint towards her.
"Keep her safe. I'll handle the Archer."
Rider is beside me one second and gone the next. She runs off towards the direction that the arrow came from while I close the distance to Sakura, coming to a skidding halt.
Her face is smeared with blood and her hands are painted red with it. She even got some on her clothes, but I can't find the wounds that it came from. Around her, there are four men that look like they were ripped to shreds. I'm pretty sure that not all parts of them are still around. Bits and pieces are missing as if something has been chewing away at them. The way they look, if we had come only a moment too late, Sakura wouldn't be standing anymore.
I close my arms around her and squeeze her body as tightly as I can.
"Oh, Sakura. Sakura, I thought... I thought you were hurt."
At first, she doesn't react. She's stiff and silent.
A stray arrow whizzes past, not far from us and that seems to snap her out of it.
"Shirou?"
"Yes, I got you. I'll get you out of here."
"Shirou, I- I'm sorry. I-"
"It's fine, Sakura. You were sleepwalking. I'll explain later. For now we need to get out of here."
She looks around at the dark park, at Illya standing a bit a away, almost warily, at the darkness where Rider is presumably fighting some other Servant, and finally at the corpses surrounding us. Her eyes widen. The urge to take her away from here strengthens. This isn't a sight for women to see.
"No, Shirou, I-!"
She doubles over in my grasp. So she is wounded after all. I have to do something to get her out of this place and to a doctor.
She's clutching her hand with the Command Seals and I try to get a look at it. Maybe it's broken.
But her Command Seals flare red, not from blood but from their magic, and then they're gone.
With them goes my last bit of confidence in the future. In its stead, a certainty takes place within my heart. I have failed. I could not protect Saber. I could not protect Tohsaka. And when I forsake protecting anyone but Sakura, I could not protect her.
I will keep fighting until I drop. There is no going back, no matter what.
But deep down, at this point, I am certain that I have already failed through and through.
"Rider!"
Her scream tears through the night and breaks my heart.


Intermission: Fake Priest
The fake priest watches the events that he will eventually have to clean up and conceal as they unfold. The grotesque being haphazardly fused together by the counterforce attacks the broken grail as it tries to feed itself. Oh how he wishes he could have seen Rin Tohsaka's final moments.
He wonders if she went quickly or if it was a drawn out business with tears and screams and many exciting facial expressions. A chuckle escapes him, but he suppresses it soon. Better not to be seen by that abomination. Who could predict what it will do to him, considering the state his body is in. And then there's the other issue. What if there is still some part of Rin or her Servant jumbled into the personality of that thing? What if it decides to get vengeful for whatever reason. No, he is fine just watching from the shadows. He always has been.
The Emiya boy clutches the Matou girl to him, not knowing what it is he is protecting. Although, Kotomine isn't quite sure if there isn't the slightest hint of knowledge.
"Sneaking around in the shadows isn't very priestly, don't you think? And neither is that smirk."
The proper vessel has decided to come as well.
"Why aren't you intervening yourself? You must have figured out what they did to her by now. Aren't you upset that she stole your function as the grail?"
He looks down at the tiny girl next to him. She looks so much like her mother and luckily nothing like her father. If she did, he wasn't sure if he could contain himself.
Illyasviel von Einzbern's face is filled with sorrow, but at the same time shows a sad sort of determination.
"I couldn't tell him. I didn't need to. The Counter Guardian will take care of it and if I had told him, it wouldn't have changed anything. It just would have made him more unhappy."
This troubles Kotomine. He would have preferred to see the boy's face as he fights for the girl, fully knowing that it is a monster he is giving his life for. Everything is just so close to being perfect, but all those little details are causing the whole thing to be somewhat dissatisfying.
The girl screams her Servant's name one last time and while the two of them are busy fussing about the missing command spells, the Counter Guardian takes to the stage with far too long strides.
The image is one of perfect magnificence. Rin Tohsaka's body has been defiled to the core. Bits and pieces of her Servant have been added to create a disproportioned monster with elongated arms that bend not just once, but twice.
But much more beautiful than the mismatched limbs is her face. It is blank and at the same time radiating pure hatred. Hate for the sister she once must have loved. There is no pain at the prospect of killing her. In front of him is a glorious machine of murder that once used to be his charge.
He wishes he could show the little Rin from his memories this distorted image of herself and delights at the terror he is sure she would have felt.
Without any warning, the Counter Guardian projects arrows upon arrows, firing them like a machine gun. Emiya holds out his arms as if to save Matou from the onslaught. What a foolish boy.
Instead, a black shadow appears to swallow the barrage before it skewers either of them. Its tendrils rush at Rin causing Emiya to whip around, sweet, sweet betrayal on his face. Matou is crying.
Rin dodges the shadow with agility that goes far past what he has ever seen a regular Servant achieve. The feat is much more impressive considering the way she looks like she shouldn't be able to take a single step with those legs without falling.
There is an eldritch elegance in the way she moves those long limbs without being impeded by them while at the same time firing a new volley of arrows that is again intercepted by a wall of shadow.
Being fed up with the way the fight is going, the Counter Guardian backs up with an impressive leap and prepares a more refined projection. All Kotomine can make out is that it is some sort of sword with a screw-like blade.
She fires it at the pair. Emiya is no longer turned towards Matou, but is instead wielding a faintly glowing branch now. Another chuckle escapes Kotomine and gets him a disapproving look by the Einzbern girl.
The sword turned arrow speeds at the two humans and Emiya gets into a defensive stance as if his branch will be able to deflect the Noble Phantasm.
Just before it hits, the two of them are swallowed in shadows.
A shockwave follows a massive explosion and hot air is suddenly blasting past them. The Einzbern girl coughs and puts a hand in front of her face to shield herself from the heat. Meanwhile, Kotomine can't help himself but keep staring, mesmerized.
The shadowy cocoon peels back to reveal that they are unharmed and launches into a new offensive. Next to him, the little girl gasps.
"No, she can't."
At first, Kotomine doesn't understand, but then he does.
The moonlight is sparkling off the new sword that Rin projected in all the colors of the rainbow.
"How can she project that? Archer couldn't have seen the real one!"
While the confused terror on the girl's face amuses him, he feels that he can get her to go beyond that if only he confirms that this sword is indeed the one she thinks it is.
"The blueprints to this particular heirloom were left to the Tohsaka family for them to decipher through the generations. I suppose the old man did not expect this one to gain the capacities to figure it out this fast."
He gets the desired reaction and turns back to the fight where Rin just launched her new missile at the shadow, dodging more of its tendrils in the process, before sending two more regular arrows to follow it.
The Zelretch Sword hits the ground before a newly made shadow-cocoon, exploding into a kaleidoscope of light. The glare rips through the cocoon, revealing what lies beneath. Her next two arrows follow quickly, piercing both heads with horrifying precision causing the two bodies to drop down with the boy landing halfway on top of the girl.
Both go down and the remaining shadows dissipate at once.
Kotomine feels a twinge of regret at not having been able to see the boy's face during his last moments, but that regret is quickly blown away as the Counter Guardian approaches her fallen enemies with measured steps.
"What's she doi-?"
Almost automatically, he puts a hand on the girl's mouth. He doesn't want to miss a thing of what's going on now.
Rin crouches down next to Emiya, placing a far too big and oddly tanned hand on his cheek. Her face is contorted in sorrow and she is crying. Kotomine's heartbeat picks up as euphoria courses through him. Yes, there is definitely some part of her still alive in there.
She closes her eyes to say her farewell:
"I'm sorry, Shirou."

Picture.


The following has spoilers for the Heaven's Feel Visual Novel:
So, how the hell does this happen? The way I see it, this turn of events fits into a Heaven's Feel route where Shirou simply was too nice to Tohsaka in the wrong route, so that she took the hit from the shadow for him. Her Servant obviously tries to save her and both end up dead with parts of them irreversibly deleted by Sakura's imaginary space. This also means that Shirou doesn't lose his arm and with Archer and Tohsaka gone, the Counter Force makes an appearance, because suddenly all the big players that could stop the Mango are gone. That's where this story starts.