What happens when you summon Emiya Shirou in Chaldea

Muramasa Returns

"So, let me get this straight. You want to see Sengo Muramasa?" Shirou asked.

"Yes. That's exactly right Shirou," Merlin said.

"But why? Why do you suddenly want to meet Muramasa, Merlin?"

"Well, the story between you and him interests me. While I have heard of the concept of a heroic spirit possessing a mortal body, it usually ends up with the heroic spirit taking possession of the body. However, in your case, you managed to retain your mind while gaining Sengo Muramasa's skills. Not only that, but you are able to communicate with Sengo Muramasa as well in your reality marble while he also shares your body by residing in your reality marble."

"I see. But why are you asking me? Why not ask Mashu since she's the same as me?"

"Well normally I would, but...she's out with master now."

Shirou let out a small sigh. "Figures..."

"Anyways, would you help me grant this flower mage's request, Queen Shirou?" Merlin asked with a smirk.

Shirou sighed again. "Just give me a moment to see if Muramasa is okay with that idea of yours," Shirou said.

Merlin let out a smile. "Great! Now go and ask him!"

"Will do. Just let me activate my reality marble for a moment..." Shirou said as he closed his eyes and began to activate his reality marble.

"Ah wait. Not like that," Merlin interrupted him.

Shirou was confused. "What do you mean by that?"

"Well...I want him to possess your body for a moment."

Shirou was surprised for a moment before saying, "Huh?!"

Muramasa was relaxing in the copy of the Emiya Residence, looking at the clear blue sky of the reality marble. "Wow, what a great view my host's reality marble has. A clear sky, a lush green field of various flowers, and most importantly...there are swords everywhere for me to study. Speaking of which, I wonder what is that giant contraption my host traced a while ago?" he thought as he then turned to the Strike Freedom Gundam in the corner nearby the Emiya Residence. "Even now that giant contraption still confuses me. I've never seen this type of thing before in my lifetime."

As Muramasa continued looking at the Strike Freedom Gundam, he felt a familiar presence coming in. He then turned around to see Emiya Shirou. "Hey there Shirou."

"Hey there Muramasa," Shirou said as he sat down on the porch.

"So. What brings you here? You got into trouble again and need my advice?" Muramasa jokingly asked.

"Nope. Rather, it's a request from Merlin."

"Merlin? Who's that? Is that somebody new?"

"You already seen him before. White hair, white robes, carries a wooden staff? Remember?"

"Oh yeah. I remember seeing a fellow that matches your explanation. It was during that time when you brought a lot of people here for your noble phantasm testing."

"Yeah...along with that was when I beat the King of Heroes."

Muramasa let out a chuckle upon hearing Shirou saying that. "Hah! That arrogant golden brat had it coming! I take it that word has spread about that event?"

"You have no idea. After that event was spread throughout of Chaldea, nearly everyone at Chaldea wanted to meet me because of either wanting to have a sparring match against me or wanting to look at Tsumugari Muramasa. Not only that, but I have been receiving requests to join parties from other servants, especially the Japanese servants. They consider me as their inspiration because of how I beat the King of Heroes with your noble phantasm."