"Hmmmmmmm..." Okita Alter said as she was laying down on the couch lazily while looking at the ceiling above her.

"What is it Alter me?" Okita asked with a sigh.

"Well...I've been thinking about something."

"What is it?"

Okita Alter let out a small sigh before answering her non-altered counterpart's question. "I wonder what happens when Shirou uses Tsumugari Muramasa."

Okita was confused with her altered counterpart's question. "What do you mean by that?"

"Think about it. Shirou is a saber-class servant, which means he uses a sword as his noble phantasm, well one of his noble phantasms, correct?"

"Well yeah, but what does that have to do with your question?"

"Well, it got me thinking, what does Shirou do when he uses Tsumugari Muramasa? Every of the saber-class servants that I've seen would have their noble phantasms either be having a giant beam from the sword or a sequence of sword strikes. However, I don't know what kind of attack Shirou's Tsumugari Muramasa is. Even during that time where all of us witnessed Tsumugari Muramasa in action, we weren't able to see it because of the pillars of flames."

Okita let out a sigh. "Really? That's the thing that was on your mind?" she asked.

"Yeah. Doesn't it bother you too?" Okita Alter asked.

Okita scoffed. "No, it doesn't," she replied. "Although she does have a point. Even after Shirou-san's demonstration of Tsumugari Muramasa, I still don't know what kind of attack it was. All that we know of is that it's an anti-reality noble phantasm that can purge resentment, cut through bonds, fate, causality, and destiny, and slice through the idea of karma itself. Not to mention the fact that it can destroy a reality marble itself. Just what is it?"

As both Okita and Okita Alter were thinking about it, it was then that a servant came into the room they were in.

"Hey there Okita! Okita Alter!" Musashi exclaimed happily.

"Hm? Oh, hey there Musashi-san!" Okita said.

"Hey there Musashi..." Okita Alter said.

"So, what were you two talking about?" Musashi asked as she sat down on a nearby chair.

"We were talking about what the Tsumugari Muramasa is," Okita Alter replied.

"Eh?! One of Shirou-kun's noble phantasms?!" Musashi asked excitedly

"Yes."

"Okay. Why were you talking about it?"

"Because I really want to know what kind of attack it unleashes. Musashi, your noble phantasm unleashes a beam right?"

"Yeah, and your noble phantasm is a flurry of slashes with a beam from your sword in the end, right?" Musashi asked.

"Yes. The same goes for my counterpart as well, minus the beam part. Anyways, this is where the problem begins. I don't know Shirou-san does with Tsumugari Muramasa. I mean, what happens when he swings his sword? Does a beam come out? Or is it something else that I have never heard of? Doesn't bother you Musashi?" Okita Alter said.

Musashi then gave Okita Alter's question and long thought and said, "Well, now that you mentioned it, you have a point. Back in Shimousa, I don't know what kind of attack Tsumugari Muramasa was when gramps used it. To be fair, I didn't see it back then. And when Shirou-kun used Tsumugari Muramasa, we weren't able to see what it was because of the blinding light from the clash between him and the arrogant so-called King of Heroes."

Okita Alter let out a sigh. "I see. So even in Shimousa, you couldn't see Sengo Muramasa use Tsumugari Muramasa himself?"

"Yes..." Musashi said with defeat in her voice.

"Well, guess we don't have any leads on this then..."

Okita Alter and Musashi let out a sigh as they were trying to solve the mystery behind Tsumugari Muramasa and what happens when Shirou or Muramasa uses it. Meanwhile Okita was dumbfounded at both her altered counterpart's and Musashi's thinking.

"Seriously? They're having a conversation about Shirou-san's other noble phantasm? Well to be fair, the Tsumugari Muramasa is practically the strongest noble phantasm here in Chaldea in which it not only beat the arrogant King of Heroes' noble phantasm, but it also cut his arm off in the process. It's so well known that nearly everyone here in Chaldea knows about it and among the Japanese servants, it's known as our greatest treasure considering its value among us, even if it is a Muramasa blade. But still, doesn't my altered counterpart have something else to think about? And even now, I still can't believe she's Miyamoto Musashi, the famed swordsman in all of Japan. The Miyamoto Musashi that I knew was a man and wasn't this relaxed and easygoing as well."

As Okita Alter and Musashi were grumbling about what kind of attack Tsumugari Muramasa, Musashi suddenly got out from the chair she was sitting on and was leaving the room.

"Musashi? Where are you going?" Okita Alter asked.

"Isn't it obvious?! I'm going to where Da Vinci is!" Musashi replied.

"Da Vinci? You mean that genius inventor?"

Musashi nodded in reply.

"Okay, but why?"

"To see if she has any footage of that duel between Shirou-kun and that arrogant King of Heroes! She was there with us during the match and she did say she needed data on Shirou-kun's noble phantasms. Therefore, she must have some footage of the whole thing don't you think?"

Okita Alter thought about what Musashi said and replied, "You do have a point there. She was gathering data over there at the time, so she should at least know what kind of attack Tsumugari Muramasa is."

"Great! Let's go then! Follow me!" Musashi excitedly said as she left the room with Okita Alter following her.

Okita let out a sigh as her altered counterpart was onto something crazy again. "Wait up!" she said as she got off from the couch she was sitting on and followed both her altered counterpart and Musashi.

Da Vinci was in her workshop, relaxing on a chair while enjoying one of her favorite past times, which was drinking coffee from her favorite cup. "Mmmm...today seems to be a quiet day. I have nothing on my mind for the moment, so for now, I'll just sip on my cup of coffee. Maybe I'll rewatch some of the DVDs Ritsuka has gave me a while ago..." she thought as she sipped on her cup of coffee.

However, as she was sipping on her cup of coffee, there was a bunch of sounds coming from her front door. "Well then, wonder who that could be?" she thought as she stopped drinking from her coffee up and headed towards her front door to see who was knocking on it. As she opened it, her guests appeared in front of her.

And they were Okita, Okita Alter, and Musashi.

"Hi there Da Vinci-san," Okita said.

"Hi there Da Vinci," Okita Alter said.

"Hi there Da Vinci!" Musashi said happily.

"Hi there Okita, Okita Alter, Musashi," Da Vinci greeted with a smile on her face. "What can I do for you three?"

"Well, me and Musashi are here to ask you for something," Okita Alter replied.

"And I'm here to make sure she doesn't do anything crazy," Okita replied as she mentioned her altered counterpart.

"Really? What are you asking me from me, the great genius Da Vinci?" Da Vinci asked joyfully.

"Well...do you know what kind of attack Tsumugari Muramasa is," Musashi replied.

Da Vinci was both confused and surprised upon hearing Musashi's answer. "You two wanted to know what kind of attack Tsumugari Muramasa is?" she asked to Okita Alter and Musashi.

"Yes," Okita Alter and Musashi said in unison.

"Why though? Weren't all of you three present during that practice battle where Shirou unleashed Tsumugari Muramasa on the King of Heroes?"

"Yeah, but the clash between the two were so bright we weren't able to see what kind of attack it was," Okita Alter said.

"Exactly. The only thing that we know is that it is an anti-reality noble phantasm that is able to cut through a reality marble with ease. But we don't even know what it looks like," Musashi said.

"I see...so the reason why you two are asking me is because since I took data from that match, you two were hoping that I have at least some footage of what it looks like?" Da Vinci said as she connected the dots together.

"Yes. That's exactly what they're here for Da Vinci," Okita replied with a sigh.

Da Vinci let out a sigh as well. "Well, I suppose I could show you at least. Just come inside," she said as she went back into her room.

Okita Alter and Musashi got excited upon hearing that Da Vinci has footage of the battle and quickly headed inside while Okita let out a sigh following them.

"Gosh those two...but at least I'll know what happens when Shirou-san uses Tsumugari Muramasa..."

Soon, Da Vinci headed over to her computer with Okita, her altered counterpart, and Musashi following her. As she got to her computer, she then checked her computer files to find the file that holds Shirou's use of Tsumugari Muramasa. Eventually, she found the file they were looking for and opened it up.

"All right. Here it is," Da Vinci said as she opened the file up, showing the video of the fight between Shirou and Archer Gilgamesh. Soon, Okita, her altered counterpart, Musashi, and Da Vinci started to watch the entire fight. Eventually, they reached to the part they wanted to see.

The scene where Shirou unleashed Tsumugari Muramasa on Archer Gilgamesh.

They were watching the scene with anticipation, hoping to see what was going to happen when Shirou used Tsumugari Muramasa.

"Here it is! The scene where Shirou-san/Shirou-kun unleashes Tsumugari Muramasa!" Okita, her alter counterpart, and Musashi thought as they famous slash was about to happen. What they expected was that a giant beam was emitted from Tsumugari Muramasa considering the condition and situation Shirou was in.

However, to their disappointment, the video didn't show what Tsumugari Muramasa was as the light of the clash between the two was too bright to record.

"Dang it, it's too bright to see..." Okita Alter thought.

"The light blinded the camera too huh? Well, that was expected..." Okita thought.

"Aw...I want to see what happens when Shirou-kun uses Tsumugari Muramasa..." Musashi thought.

"Um...Okita, Okita Alter, Musashi? Are all of you okay?" Da Vinci asked, snapping the three out of their thoughts.

"Hm? Oh, yeah. We're just a little disappointed that we didn't get to see it..." Okita Alter replied.

"Yeah. I wanted to know what it looks like..." Musashi said.

"Me too..." Okita muttered softly so that no one ever heard her.

"I can see why. All of you were expecting something to come out, right?" Da Vinci asked.

"Yeah..." Okita, her altered counterpart, and Musashi said in unison.

For a moment, Okita, her altered counterpart, and Musashi were struggling with the fact that Tsumugari Muramasa was a single sword swing and were trying to figure out if there was any secret behind it.

After a few more minutes of thinking, Da Vinci suddenly have an idea that came into her head.

"I have an idea!" Da Vinci said with a smile on her face.

Shirou let out a sigh at the situation he was in. Right now, he was in Chaldea's testing room along with Da Vinci, Okita, her altered counterpart, and Musashi were looking at him. "This definitely feels like déjà vu. It's like the day where Da Vinci asked me to show her my noble phantasms. In fact, this is practically the same, but with less people!"

"Hey Shirou! Are you okay there?" Da Vinci said.

"Yeah. I'm fine Da Vinci. Although is this necessary? I mean, you already have data on my noble phantasms, so why am I doing this again?" Shirou replied.

"Because Okita Alter and Musashi wanted to know what Tsumugari Muramasa looks like when it is unleashed!" Da Vinci replied.

Shirou was in disbelief at the answer Da Vinci said. "Really? Is that the reason why you dragged me earlier and forced me to do it?"

"Yes!"

Shirou let out a sigh. "Well...is the room at least able to handle the damage Tsumugari Muramasa can unleash? I don't want to damage Chaldea."

"Relax. I upgraded the room for situations like this," Da Vinci said with a smile on her face as she was confident that the room was ready for something like this.

"Hurry Shirou-kun! I want to see what happens when you use Tsumugari Muramasa!" Musashi said excitedly.

"Yeah. Show it to us now," Okita Alter said.

Okita let out a sigh. "Don't mind them Shirou-san. They're just excited to see you use it."

"Figures...well, might as well get this over with. Although I'm pretty sure that if Arturia and her counterparts find out about this, I'm going to get scolded for this..."

Shirou then unsheathed his katana.

"Let's hope this doesn't end badly..."

(Meanwhile...)

Ritsuka was walking in Chaldea's hallway, minding his own business.

However, his peaceful walk was interrupted as he heard a giant sound nearby. Worried if somebody attacked Chaldea, he then hurried to the source of the sound. "What the heck was that?!" Eventually, he arrived at the source of the sound, which was the testing room.

As he opened the door to see what was going on, what he saw gave him a shock.

The training room was heavily damaged as there was a giant gash on the wall that looked like a slash from a giant sword along with multiple holes on the ground. However, there was no giant sword as he looked around the room to see Shirou, Da Vinci, Okita, her altered counterpart, and Musashi in the room.

For a moment, there was silence between them. Then Ritsuka spoke out.

"So...Shirou, care to explain what just happened?" Ritsuka asked as he was shocked with the scene in front of him.

Shirou sighed. This was going to be one long explanation he was going to have to explain...

"So let me get this straight, Okita, Okita Alter, and Musashi wanted to know what kind of attack Tsumugari Muramasa is, which resulted in Da Vinci dragging you to the testing room, resulting in this?" Ritsuka asked as he got the geist of what happened.

"Yes," Shirou replied.

"I see." Ritsuka then turned to Okita, her altered counterpart, and Musashi. "Were you three satisfied with the result?"

"Yes," they said in unison.

"Well, what was it?"

All three of them were silent for a moment before saying their answer.

"It was a simple sword swing."

1/1/21 update: Added a few things because of the release of Muramasa.