Assassin was a man named Shirou Emiya. In another history, the Grail caused mass destruction at the end of the Fourth Holy Grail War. Shirou lost his parents in the destruction and was on the brink of death, but was saved by Kiritsugu Emiya who adopted him. In this history, it was Kiritsugu who lived through the Fourth War with both Irisiviel and Artoria dying in the chaos. Kiritsugu didn't live to see the Fifth War, but Shirou did and became a Master. He summoned Artoria and they ended up destroying the Grail after learning of its corruption. Afterward the lad grew up to be a hero and he eventually died by the hand of those he was trying to save. After death he became a Counter Guardian to continue his journey to rescue all he could.
The Saber known as Rin Tohsaka was sitting on the roof of the church as she listened to Assassin explain his history to Artoria, Fujimura, and an unconscious Illyasviel in the courtyard. As he went on to explain the close relationship he had with many of the people involved in this war, including Rin, Fujimura and Artoria were confused and suspicious. That was what the crimson Servant assumed given their expressions. He was throwing out a lot of information that he apparently only fully remembered recently, so finding his claims lacking in veracity was reasonable.
Rin knew he was telling the truth given his claims were awakening the remaining sealed memories in the Saber's mind. She had known Shirou and fought alongside him to save the world. She even developed feelings for him, though they never went anywhere in her timeline, nor did it in this Shirou's life according to him. It was Artoria that he fell in love with. In the crimson Saber's life, Sakura ended up never being saved from the Matous and became the Black Grail. Rin ended up killing her for the greater good and afterward, Rin became the protege of Zelretch the Wizard Marshall. She succeeded him as the Magician of the Second Magic and eventually she became a Counter Guardian to try and save Sakura. This ended up being a futile effort. Sakura could not be freed from her torment and Rin spent the rest of her existence killing those deemed dangerous. The Guardian felt the constant murder wear away at her until all she wanted was an end to her entire being.
There was a part of the crimson Servant who felt like she should cry, but instead she was at peace. There was a catharsis at finally having her memories restored and having them pretty much be what she expected. There were still surprises, like it turning out that she knew Fujimura in her timeline, the yakuza being her teacher in high school. The Servant Rin was acquainted with almost everyone involved in this war.
Now that Rin's memories had returned in full, she could make full use of her abilities as a Servant, including her Noble Phantasms. She couldn't utilize her full potential as a Magician due to not being summoned as a Caster, but her Noble Phantasms made up for the loss. Given the mechanics of one of her Noble Phantasms, it would be possible to get rid of all the knights of Dolorous Guard, even Guinevere, without anyone getting exhausted.
Artoria and Fujimura began coming around to Assassin's story as he gave details about the both of them that nobody unfamiliar with them could know about. To be fair, he could possess an information gathering Noble Phantasm, something fitting for an Assassin, but Fujimura would already know about such a capability by now. If he had such an ability, he would have used it to locate Irisviel, which he didn't.
"Okay, I'll believe your story for now, but what does that have to do with Illya?" Artoria adjusted her hold on the unconscious homunculus in her arms. "You said you could teach her something."
"I was saved from dying in the fire at the end of the Fifth War because Kiritsugu inserted Avalon into me. Like with Illya, it altered my Origin and element to Sword. I managed to utilize those changes within me by learning projection magecraft. I became capable of tracing and projecting copies of any Noble Phantasm that had a physical form and wasn't a Divine Construct or of too high a rank. I can teach this to Illyasviel."
"No wonder you have so many Noble Phantasms, you're a counterfeiter. Are you sure you're not the Heroic Spirit of Elmyr de Hory?" Fujimura smirked.
"If you let me teach Illyasviel how to use my style of projection magecraft, I'm sure she'll pick it up quickly. She is already familiar with magecraft involved in the manipulation of matter thanks to alchemy. That will serve as a good foundation to give her a head start on learning how to trace and copy things. If this works, then she and I can handle Gilgamesh together and Archer can be free to face someone else."
"I don't know how I feel about Illya fighting Gilgamesh." Artoria bit her lip. "It's not my decision to make. You'll have to ask Illya when she wakes up."
"If she said yes to me teaching her, then she'll say yes to Assassin." Taiga said.
"I'm not so sure. I directly caused three people she loved to die in one sense or another. I think her grudge against me is a step above yours, Master." Assassin turned around and entered Spirit Form. "Let me know when she wakes up and is sensible enough to speak with."
Now that Assassin was gone, Rin decided she was done snooping and entered Spirit Form too. She passed down through the roof and into the building. She walked through the halls while thinking about what her next course of action should be now that she had recovered all her memories. Obviously she'd have to tell everyone since she was now far more powerful and possessed new capabilities. They'd need to take them into consideration when making their next strategy to dismantle the Grail.
The real sticking point was whether it would be best to bring up the finer details of the crimson Saber's life, namely how she killed Sakura. How would the living Rin and Sakura react to finding out? It wasn't just a matter of if they would think less of Saber Rin, it might make Sakura look at her Rin differently. To know that your sister was willing to kill you in another timeline, even if it was for a good cause, would be haunting to learn. Saber could try to keep the details of her life secret, but her living counterpart's inquisitive nature would leave her unsatisfied if she didn't receive the whole truth. She'd definitely want to know about what happened to Sakura in Saber's history.
"They'd find out eventually." The Servant said to herself as she found herself standing in front of the entrance to the attic Rin and Sakura called their room. She opened the door and found the sisters on their beds, Rin polishing the pendant she received from her father(or trying to at least given she only had a single thumb to use) and Sakura staring at the ceiling.
"Hi, Saber." Sakura didn't stop looking up.
"Hello." Saber said.
"What's wrong?" Rin immediately picked up on her Servant self's tension.
"I finally got all my memories back."
"Really?" Sakura stopped staring at the ceiling.
"That's great!" Rin stood up. "You know your Noble Phantasms now, right?"
"I do."
"That's fantastic! What are they?"
"Before we get into that, I have other things I have to say. You might want to sit down."
Rin did as her other self suggested and Saber began to explain the details of her life. She told the Tohsaka sisters of how Sakura was never saved in her history and became the Black Grail. Rin killed Sakura and went on to become the Magician of the Second Magic, but she was filled with so much regret over killing Sakura that she made a deal with the Counter Force in a vain attempt to save her younger sister.
"That can't be true." Rin's face was one of utter horror. "I'd never…"
The Tohsaka heir was shaking as she curled into the fetal position atop her bed. It was about what Saber expected.
"What's wrong, Rin?" Sakura asked while bizarrely poised.
"Do you even need to ask that? I killed you in another timeline. I killed you in cold blood without even trying to find another way. I killed you after you suffered even more than you did in this timeline. How heartless could I possibly be to do that? I couldn't." Rin got back into a regular sitting position again. "Saber, you might have been able to kill Sakura, but I never could. We may have started off the same, but we've developed into totally different people. I could never hurt Sakura. I don't care if the world was at stake, I'd find some other way to save her!"
"And what if you couldn't?" Sakura said.
"I could!"
"But what if you couldn't? Just answer the question." Sakura's voice was low.
"It would never come to that." Rin's foot began tapping the floorboards.
"I'd hope you'd be able to do it." Sakura's words made both Rins wince.
"How could you possibly want that?" Rin learned forward as she made eye contact with her sister. "You'd want to die?"
"If the world was at stake, then yes. Shouldn't that be obvious?" Sakura's hands interlocked. "When Saber said she killed me to save the world in her reality, it made me happy. Maybe happy is the wrong word? Relieved. It relieved me to know that my sister isn't so obsessed with coddling me that she could sacrifice me for the greater good of all humanity."
"I don't understand." Rin was quaking again.
"Of course you wouldn't." Sakura rose to her feet. "You treat me like I'm helpless without you. Even after Saber warned us of the dangers of becoming too obsessed with each other, you still wouldn't let me fight alone when we were planning our initial attack against the Grail"
"It wasn't just about protecting you, it was also the smartest way to divvy up the work. It was the best option strategically."
"And would you have left me to protect myself if it was the tactically best option? Or would you have contrived some reason why you'd still need to stay by my side?"
A second passed and Rin didn't answer. Another second fluttered away and there was still no response. Another second, no retort. Time kept ticking and each moment made it clearer that Rin had no way to refute Sakura's insinuation.
"Rin, why can't you trust me? I trust you." Sakura was shaking too now. "I put my faith in you to defend yourself when we fought Taiga and you did. You even said after you got hurt that we need to trust each other and be ready to protect ourselves. Was that a lie? Does it only go one way? You don't need my protection, but I need yours? Am I just too incompetent to take care of myself in your eyes? Am I still that little girl in the pit of worms to you?"
"Sakura, I trust you, I do." Rin held her arm out towards her sister. "I just want to keep you safe. I'm sorry, it's just that after what you went through with the Matous, I want you to live a long and happy life."
"I do too, but I want to choose what I do with that life! I should have a say in what I do!"
"You do have a say."
"Do I really? I always follow your lead!"
"I'm sorry! I'm just doing what's in your best interest!"
"Is it in my best interest? Do you even know what I need, what I want?"
"What?"
"Y'know, Saber said part of our problem was that we were so obsessed with each other that it was like we were becoming the same person, but she was wrong. You don't know anything about me. You still don't even realize that I hate our father! You still act like we both admire him and aspire to be like him! Did you forget the part where he sold me to the Matous for the sake of having a backup to carry his legacy? Did it never dawn on you that I'd be upset about that? Even if I didn't end up getting tortured by the Matous every day, I'd still despise him for treating me as just an extension of him and his stupid Tohsaka family! Now you're doing the same thing as him! You're treating me as an extension of you! When we were planning the attack on the Grail, you said you'd give me father's pendant to defend myself! You think I want that thing? I don't even wanna look at it! You just assume I've always felt the same as you about everything and that's because I've been too afraid to speak for myself! I'm the stupid, weak little girl who needs you to decide how we feel and what our opinions are! You like father, so I guess I like father too! Well fuck father, I hate him! He got what he deserved when a bullet blew his brains out!" Sakura stopped and breathed deeply in and out before continuing in an even voice. "I'm partly to blame for this. I was obsessed with being at your side and protecting you, all while never rebuking you for protecting me. The problem is that I've begun to change and you haven't."
It wasn't a surprise that Rin was crying after everything Sakura had just said. Saber knew herself well enough to know she'd never let herself lose her composure for the sake of living up to the Tohsaka name unless she was truly distraught. After seeing how little she truly understood Sakura, she likely felt like a failure. That would be how Saber would feel in her situation, at least when she was younger. Rin covered her face with the remains of her hand as she broke down.
Sakura's lips quivered as she watched her sister become overcome with her emotions. Sakura's eyes searched around the room as if for a solution to her current situation. Was this the first time she had seen her sister like this? It was clear that Sakura had used this moment as an excuse to blurt out a lot of repressed feelings she'd had, some born recently, and some that had festered for years. Now Sakura was realizing the consequences of just dropping so much upon her sister without warning.
The purple haired girl ran out of the room while leaving behind her tears.
Saber wanted to go after Sakura, but she also didn't want to just abandon her living counterpart while she was overcome with negative emotions. The crimson Saber walked over to her Master and sat next to her. For a little while the two Rin Tohsakas just sat next to each other. The human Rin leaned into her Servant who wrapped an arm around her. The weeping girl let out her grief without reserve while being comforted by the person who would be the least likely to judge her. There was a tranquility to the moment. No facades or restraint, just an honest expression of sadness that the two women basked in.
Rin began to calm down and she wiped her wet face on her sleeve.
"Are you okay?" Saber asked.
"Sakura is right. Nothing she said was wrong." Rin's voice was scratchy. "I've been treating her like a part of myself and not her own person. I thought I had moved past that when I was captured, but I guess I jumped the gun thinking I could change so easily."
"It's not like you can completely alter your habits in a few days. People are capable of change, but it's a gradual process. If it was quick, then self-improvement would be a lot easier."
"That's true." Rin sniffled. "I can't believe Sakura feels that way about father."
"Do you think she's wrong to feel that way?"
"Part of me wants to say she's wrong, but how could she possibly be anything but justified after father gave her away? Like she said, even if Sakura hadn't been tortured by the Matous, father still got rid of her so she could be a backup heir. There are understandable reasons for giving your child away, but that probably isn't one of them."
"In my life I always put the legacy of the Tohsaka family above all else. For you to prioritize your sister is surprising."
"Having Sakura come back to me after our parents died made me see just how important she was, how important people are." Rin sniffled again and Saber handed her a handkerchief. "Thank you." The girl blew her nose before continuing. "I put Sakura first from then on, at least I thought I did. I unknowingly forced Sakura to help me carry on our family legacy, so maybe I was actually putting the Tohsaka name first."
"Once again, changing is hard and you were raised by our father to value the Tohsaka name and being the ideal magus above all else. Even if you consciously resolve yourself to adjust your behavior, you will still fall into patterns subconsciously."
"I want to protect Sakura, but I also want her to have autonomy." Rin leaned her head on her wrist.
"I think you were right when you argued for you, Sakura, and I to all fight together at our initial strategy meeting. It was the smartest option given the information we had. I think Sakura was over eager to separate herself from you at the time. That isn't me saying everything she said is wrong, just that she's at a turning point in her life and so she wants to force the changes she thinks need to happen as quickly as possible. You and Sakura need to have a calm talk where you can both open up and reach some kind of happy medium."
"You're right. Now probably isn't the time. Sakura needs to calm down. We'll talk later today or tomorrow." Rin was regaining her composure.
"Sounds like a plan." The Servant pet the head of her alternate self.
Right when the moment reached a form of pleasant resolution, it was interrupted.
Presences. Five of them. A quartet of Servants just let themselves be sensed. They were using Presence Concealment, but they suddenly became able to be detected, but only barely. They were still using Presence Concealment, the rank just went down. Presence Concealment only weakened like that when the Servant in question was about to attack.
Five Assassins were about to attack. No, there were more. They were all over the church premises, it was just that five were in the room both Rins were in.
No, there was only one Assassin.
This was Hassan Alter.