That Time I Reincarnated as Shirou Emiya's Little Sister

by lunawu516

Fate stay/night x Fate Grand Order Y/n a normal high school girl died in a car accident. When she opened her eyes she was a kid again, but that's not all she looks awfully familiar. And was more shocking is that she is in her favorite Anime Fate stay/night. And she became Shirou Emiya's Little Sister. The Fate stay/night and Fate/Grand Order are owned by Type-Moon, and ufotable.

2. Chapter 1

CHAPTER 1

"Servant Shielder, my True Name is Galahad of the Revelations, one of the Knights of the Round Table. " He looked at my face.

"I ask of you, are you, My Master?"

Galahad stood up.

"Yes. My name is Ritsuka Emiya. I look forward to working with you. Galahad."

"Master, please refrain from using my True Name, for it will be a disadvantage for the Holy Grail War."

"All right, I'll call your Servant Class then."

"Yes, that would be helpful."

"And also, just call me Ritsuka if you please or Senpai if you want."

He looked at me, confused. "I can accept calling you "Ritsuka," Master, but I am confused. Why would I call you Senpai? And also, you look younger than me."

"Oh, nothing. ~"

'Because a certain someone is calling this body "Senpai."'

"Don't call me young I am way older than I look."

"How exactly?"

'Oops, I forgot that I am a child in this body.'

"Never mind. Let's work hard, Shielder." I offered my hand to him. He took my hand, and we shook hands.

"Yes, Ritsuka."

"UMU." We parted our hands.

"What shall we do from here?"

"First, we must save my sister."

"You have a sister?"

"UMU. She is a half-human and half-homunculus, the vessel for the Holy Grail. I cannot let her suffer and die, so I will manipulate her magic circuits and live as a human." Galahad looked surprised.

"And also, I promised to save her and bring her home."

"You care so much about her."

"What can I say? She's my sister, after all." I made a massive smile at him.

"I understand. I will follow your orders and win this War, Master." He bowed once more.

"UMU. It's late. I should head to bed."

"Then shall I guard you in your sleep?"

"That would help, and can you stay in your spirit form."

"Yes!" Galahad went to his spirit form, and I went to my room straight to bed.

- NEXT MORNING -

I woke up in the morning and stretched my arms upward. I remembered what happened last night. I looked at the markings in my right hand. "It's not a dream." I lowered my hand. "Shielder," I called out my Servant, and he appeared.

"Yes, Ritsuka?"

"We're going on a trip, be ready. But continue patrolling the area."

"Yes, Master!"

Galahad vanished. I stood and went to the bathroom to take a bath.

I wash my body and soak myself in the tub.

"HAAAAAH~" I stared in my command seals.

"The time has come. I will save you, Illya."

I soaked there for a few minutes, and I got out. I changed my clothes and went to the living room. I opened the door and saw Shirou cooking for breakfast.

"Good morning Onii-chan."

"Good morning Ritsuka. Just wait a bit. Breakfast will be done in a few minutes."

"Okay."

Kiritsugu came in as well.

"Good morning, Dad."

"Good morning, Dad."

We greeted him.

"Good morning to you two." Kiritsugu sat.

"Um, Dad, are you going overseas (Germany) again?"

"Yes, I will be leaving after breakfast."

"Then can I come too?"

"But-"

"Please~," I begged him with puppy eyes.

"Ah."

"And also, we promised, right?"

He remembered our promise from that night. He smiled. "All right, it's a promise." He ruffled my hair, and I giggled.

"What?! That's unfair! Why is she able to go with you?!" Shirou complains.

"Well, Dad and I promised that he would take me to another country someday. Besides, is it wrong to have a father and daughter moment?"

"Well, I-"

"And also, who would feed Taiga if you come with us."

"Huh?! Taiga can feed herself." Shirou pouts while I approach him.

"Oh, come on, Onii-chan, you can have Father and son moments together after we come back. And also, I will bring a gift for you, so don't be jealous."

"...F-fine."

I hugged him, and I placed my head in his chest. "Thank you, Onii-chan!"

"I got it. I got it."

I face him while still hugging him.

"I love you, Onii-chan!"

I said that with a big smile.

SHIROU POV

"I love you, Onii-chan!"

"I love you, Onii-chan!"

"I love you, Onii-chan!"

"I love you, Onii-chan!"

"I love you, Onii-chan!"

"Onii-chan!"

'Ugh!'

Those words were pierced in my heart, and they kept echoing in my mind.

'She's so cute! I have to protect this smile.'

"Onii-chan?"

I snapped back to reality.

RITSUKA POV

"Onii-chan?"

"Uh, nothing."

"Hmm?"

"Gooooooooood morning!" Fuji-nee arrived, and she looked at the scene. "Huh? Did something happen?"

"Hi, Fuji-nee."

So I told her that I was leaving with Kiritsugu for a few days. After I told her, she suddenly hugged me tightly, rubbed her cheeks in mine, and started crying.

"Noooooooooo don't goooooo!"

"Fuji-nee, please, It's just a couple of days. I'll be back before you know it."

"No! I don't want my little Sister to go!"

'Now she's acting like a child.'

"I'll be fine since Dad is with me and Onii-chan is here with you. So Onii-chan can still cook for you." She lets go immediately.

"Okay, you can go." She said with a thumbs up.

'She immediately gives up for food.'

"That settles it. Ritsuka, go pack your stuff." Kiritsugu spoke.

"Okay, Dad!"

"Eat first before you do that," Shirou spoke.

"Okay!"

Fuji-nee joined in, and Shirou served the food on the table.

- THREE HOURS LATER -

We are now at the airport. Shirou and Fuji-nee came along to bid us goodbye. Right now, I was being hugged by Fuji-nee again.

"I'm going to miss you..."

"Fuji-nee, It's just a couple of days." Finally, she lets go of me.

"Be careful out there, okay. Don't talk to strangers if they give you candy or money. Kick their asses and run away."

"Language!" Shirou shouted while I chuckled.

"Fuji-nee, seriously, I'll be fine."

"Oh, I'm just being worried."

"Be careful, Ritsuka," Shirou spoke next.

"UMU!" I hugged my brother. "I'll be back."

"Yeah." I let go and went to Kiritsugu's side. "Take good care of her dad and come back safely."

"Yeah, Ritsuka, let's go."

"Hai!"

We started walking, and I looked back at them.

"Bye-bye!" I waved goodbye to them and rode the plane.

'Shielder, you there?'I called my Servant, who is in the Spiritual Form.

'Yes, what is it?'

'I was planning to introduce you to everyone, but don't worry. I'll come up with a name for you. Since you can't always be in your spirit form.'

'Hmm...Is it necessary?'

'Yes, and also I can't always call you "Shielder" when you materialize, and also you won't have to limit your senses while protecting me. And don't worry about draining mana; I have plenty.'

'Hmm...All right, you have a point. So, what will it be?'

'Hmm...How about Romani Archaman?'

'Wow, that's a good name, but somehow it felt nostalgic.'

'Oh really.' 'Well, that's the name from the doctor I knew.'

Author: This is the only name you can come up with, out of all the names.

Ritsuka: Shut up, Author.

Author: Whatever.

'Master?'

'Ah, yes?'

'I was just asking how to save your sibling.'

'Oh, right, I forgot.'

So, I told him the plan while we were on the plane.

- A FEW DAYS LATER -

Galahad and I arrived in the Einzbern cattle in Germany. I asked Kiritsugu to wait in the car. At first, he insisted on coming along, but I told him I could handle it. He had his doubts, but he trusted me anyway. Galahad was wearing a black suit as Saber wore in Fate/Zero. I saw the cattle within the horizon.

"Woah! So cold..."

'Why did they have to live in such cold weather in the middle of nowhere?!'

"Ritsuka, it's too cold out here for you. Let us retreat for now."

"No! We came all this way. We can't turn back now."

"But if you stay out here, you will be freezing to death."

"Then we must save her before that happens." I look at him with a smile on my face.

He sighed. "All right, let us proceed to your plan."

"Yeah!"

We proceeded as planned. Galahad will look for Illya's room with the description I mentioned on the plane. He found her in the nearest window, he told me her location and went there quietly.

"Shielder, create a distraction."

"Hai Master!"

He summonsed his shield and went to the front door while I went to Illya's location.

- GALAHAD POV -

"HAAAAAA!"

I swung my shield and hit the front door.

*CRASH*

"What?! What's that?! Who are you?!" Shouted by a homunculus.

I punched him, and he ended up unconscious.

"Who goes-" Before he could finish, I kicked the next one to arrive.

"An Intruder! We have an Intruder!" Another homunculus shouted, alarming the others.

'Good, with this distraction. Master can sneak in without a problem.'

"Who dares to attack the Einzberns?!"

A man appeared. Like Master's description, he is an older man with long hair. I readied my shield as he approached.

'Master, the individual you spoke of, has appeared, hurry!'

- RITSUKA POV -

'Master, the individual you spoke of, has appeared, hurry!'

'Got it!'

I proceeded to sneak into Illya's room. I reinforced my legs and jumped to her balcony. When I arrived, Illya was sleeping on her bed. I opened the door and went in. Then a strong wind went into the room that made her wake up.

"Who, who's there?!" Illya yelled.

"Um, it's okay. I won't hurt you. I am a friend."

"Who are you?! What are you going to do with me?!"

"My name is Ritsuka, and I am here to take you to your dad."

"Daddy?"

"Yeah! Your Dad's name is Kiritsugu, right?"

"Yes, but Grandfather said he abandoned me."

"No, he didn't. Your Grandfather lied to you. Kiritsugu comes here every day to get you. He would never rest until he gets you."

"Daddy did?"

"Yeah! He misses you, Illya. He's always worried about you."

"Where is he now?"

"He's waiting in the car. He can't come because I told him to."

"Really?!" She shouted happily.

"Yeah! You can be together again."

"I'm glad."

Suddenly the whole cattle went to shake.

"We don't have much time. Come on. We need to go."

"Wait! There are people I want to bring with us."

"Who?"

Then the door of the room banged open, and two figures appeared.

"Lady Illya, are you all right?!"

"There is an intruder who came in here. We've come to rescue you."

'Oh, it was Sella and Leysritt.'

"An Intruder!" Leysritt pointed her ax at me. She was about to attack me, but Illya blocked her.

"Wait! She's not here to hurt me."

"But miss."

"She came here to take me to Kiritsugu. My Grandfather lied to me that Daddy abandoned me."

"How can you trust her? You only just met."

"I trust her because I can tell that she's not lying."

Sella stared at me.

"I did not come here to harm Illya. I came here to rescue her. I swear that I am not lying to all of you in my life. If you still do not believe me, come with us."

"Yeah! You should come with us."

"All right, then we will come with you," Leysritt spoke.

"Leysritt?!"

"Do we have a choice?"

Sella gritted her teeth. "Fine! If that is what milady says, then I am coming!" Then she pointed at me. "But if she tries to do something to milady, we will not hesitate to attack you."

"Okay, I'll be sure to remember that."

Then the whole buildings start to shake again.

"Come on. We have to go!"

"""Right!"""

We escaped through the balcony and ran through the forest. I called my Servant.

'Shielder! I'm done with my part. You can retreat now.'

'Hai Master!'

GALAHAD POV

'Shielder! I'm done with my part. You can retreat now.'

'Hai Master!'

I looked back to the head of the Einzbern family. That is now lying in the ground.

"You're a Servant. Why did you attack us? The Holy Grail War hasn't started yet."

"Forgive me, but I have no obligation to tell you that."

"Have you come here to kill me?"

"No, my master's objective was not to kill you."

I found the catalyst that my master instructed me to take, and I picked it up.

"Now my job is done." I turned back and walked away.

"Wait! Don't take that-"

"I prefer that you stop talking." I stopped walking and turned my head to face him.

"This is my warning if you try to harm my master. I won't hesitate to kill you. Be grateful that my master wanted you to live." He went silent. "This is a goodbye then."

I left him while his still dumbfounded and reunited with Ritsuka.

- RITSUKA POV -

We waited for Galahad before we went to Kiritsugu.

"Ritsuka, I have returned." Galahad arrived.

"Shielder!"

"A Servant?!" Sella yelled.

Leysritt was about to attack Galahad, but I stopped her.

"Wait! He's not an enemy. He's an ally."

"Are you sure, Ritsuka?" Illya asked.

"Yeah."

Sella and Leysritt lowered their guard, and Galahad decided to introduce himself.

"Forgive me if I startled you all. As you said, I am a Servant, and my class is 'Shielder,' but you can call 'Romani' for now."

"Shielder? " Sella and Leysritt spoke.

"Ritsuka, is he your Servant?" Illya asked.

"Yeah, although Romani is not his real name, it's pretty convenient too."

"Wow! This is the second time I met a Servant like him."

"Second time?" Galahad wondered.

I ignored him and approached Sella. "Um, Sella, I have a favor to ask."

"What is it?"

"Is it possible that you can hire Shielder?"

.

.

.

.

.

"Master, are you trying to sell me out? That hurts my feelings, you know."

"Wait! Sorry, that didn't come out right. What I mean is I want him to pretend that he's a butler or something from the Einzberns." I panicked while waving my hands.

"Why would you think that?"

"Because I don't want him to be discovered by Kiritsugu that he's a Servant, and it is more convenient to have him around more than in his Spirit form."

"Hmm. Well, you have a point."

"So, what do you think?"

"All right, I'll approve of that."

"Thank you very much." I bowed to her, and I looked back at my Servant.

"I'm sorry that I said that."

"Apology accepted."

"We should get out of here. Before your grandfather realizes that your gone, Illya."

I spoke to them, to which they all nodded in agreement. We all started running again. Illya was carried by Leysritt, while my Servant brought me. We can see the car up ahead along the way, and Kiritsugu was standing there waiting. Illya saw him, and she had tears in her eyes.

"Daddy!"

Kiritsugu heard her and ran toward us.

Leysritt put down Illya, and she started running to him.

"Daddy!"

"Illya!"

They both hugged each other as they missed their embrace of one another. Kiritsugu poured into tears as well.

"Daddy, I missed you!"

"Me too. I'm sorry I couldn't get you before."

I look at them with a smile on my face.

'Finally, they reunited again.'

Galahad put me down as well. Kiritsugu and Illya let go of each other. He looked at me.

"Ritsuka, thank you."

"No problem."

Now he looked at the two Homunculus and my Servant (Butler).

"And you three are?"

"My name is Sella, and this is Leysritt. We serve Illyasviel-sama. It's an honor to meet you, Kiritsugu-same." Sella and Leysritt introduced themselves and bowed.

He turned to Galahad.

"And you are?"

"My name is Romani Archaman. I am also a butler from Einzberns. I am not a homunculus, but I also serve Illyasviel-sama." He bowed as well while introducing.

'Wow, he's a good actor.'

"Likewise, and thank you for taking care of my daughter."

"We are very welcome."

He looks at Illya again. "Let's go home."

"Yeah."

We rode the car and went straight to the airport to go back home.

- WHILE ON THE PLANE -

I was reading a book when suddenly Illya approached me.

"What is it, Illya?"

"I've been meaning to ask you. What is your relationship with my dad?"

"Oh, that. Kiritusgu is also my dad."

"What?!"

"Wait! Just hear me out. Kiritsugu adopted me."

"Ohhh."

"You see, Kiritsugu saved me, and he asked me along with my brother to come to live with him."

"Brother? You have a brother?"

"Yeah, my brother's name is Shirou. He is older than me."

"Ohh."

"But you can call him Onii-chan since we're sisters now."

"Oh, I like that."

"Then I'll call you Onee-chan."

"Onee-chan?"

"Well, you're older than me, making you my big sister."

"Ohh."

"It's nice to meet you, Onee-chan!"

- ILLYASVIEL POV -

"It's nice to meet you, Onee-chan!"

"Onee-chan!"

"Onee-chan!"

"Onee-chan!"

"Onee-chan!"

'Ugh!'

I clenched my chest as the word kept repeating in my head.

'What is this feeling?'

I looked back at her. Which she seems like she's sparkling.

"Hmm?"

'She's so cute! I want to keep her!'

"Onee-chan, are you all, right?"

I snapped back to reality.

- RITSUKA POV -

"Onee-chan, are you all, right?"

"Ah~, I'm all right."

"Hmm?"

"Well let's get along Ritsuka."

"Hai Onee-chan."

"Hehehehe. "

Without us noticing, Kiritsugu was watching us, and he smiled.

- A FEW DAYS LATER -

We arrived at our house and got out in the car.

"WOW! So big! So this is Daddy's House!" Illya shouted in excitement.

"Welcome to your new home. Come on, Onee-chan, I'll show you around."

"Yeah!"

I took Illya's hand and went inside.

"No running in the house."

"Hai! "Illya and I said while I brought Illya in the living room wherein Shirou was there.

"Tadaima!"

Shirou saw me except Illya.

"R-Ritsuka?"

"Tadaima, Onii-chan." I greeted him with a smile, then he ran towards me and hugged me.

"Welcome Home. I missed you."

"UMU, I missed you too."

Then Illya approached Shirou.

"Hehhh, Ritsuka, is he the one you're talking about last night? You two looked the same."

"Huh?" Shirou looked at her.

"Yes! He is Shirou Onii-chan." I pointed at my brother.

"Um, Ritsuka, who is she?"

"Um, she's-"

"I'll take it from here." Kiritsugu came in.

"Oh, hi, Dad."

"I'll tell you about that."

Sella, Leysritt, and Shielder (Romani) came in as well. We settled down except for the two homunculi and my Servant.

[INSERT PIC]

"Shirou, let me introduce this is my daughter."

"Good morning, my name is Illyasviel von Einzbern. It is nice to meet you, Shirou, finally."

"You're my little sister?"

"WRONG! Illya is your big sister." Illya yelled at him.

"Ah, okay... Really?"

"Shirou, the truth about those overseas trips I've done. I've been trying to bring back Illya. I'm sorry, I should have told you earlier. It must be shocked to you." Kiritsugu told him the truth.

"I'm sorry, Onii-chan, that I kept it from you." And I apologize to him.

"W-... well, it is a surprise, but I didn't ask you about it either, and you shouldn't look so sad. Anyway, she's going to stay here from now on. That's fine with me." Shirou blushed while he said that. Then Illya continues to stare at him.

"Wha-what're you looking at?"

"Hmmmmm... this is... my little brother... Yes, that'll do from now on. Your big sister Illya will take care of it if you need anything!" Illya answered him. Then she looked in my direction. "That applies to you, Ritsuka!"

"O-okay... " Shirou and I both answered.

'What's with new revelation?'

"Gooooooooood morning!" Fuji-nee barged in and saw me.

"Ah, Ritsuka-chan your baaaack!"

Then she launched at me, hugged me so tight. I can't even breathe from this hug.

"Waaaaaaaahhhhhh! I missed you, Ristsukaaaaaaaa!"

"Air... Fuji-nee air."

"Hey! Let go of my sister!" Illya shouted at Fuji-nee that it took her attention.

"Oh, what's this? A newcomer I haven't seen before." She freed me and went to Illya. She looked close to her.

"Wait, you said sis-" She looked back at me and looked back at her.

"Ehhhhh?! Kiritsugu's daughter?! So that means you're Shirou and Ritsuka's Little Sister!"

"BIG SISTER!"

"Fuji-nee, she is one to two years older than Onii-chan and me."

"Oh really? Sorry about that, what is your name? My name is Taiga Fujimura, by the way."

"My name is Illyasviel von Einzbern just call me Illya if you want."

"Illya-chan... Wait, your last name isn't Emiya."

"Well, it was my mommy's last name." Kiritsugu became sad after he heard that.

"Ohh, I get it. Then it's nice to meet you, Illya-chan." Fuji-nee said.

"Nice to meet you too."

The two homunculi and my Servant introduced themselves. We live as a big happy family.

- ONE MONTH LATER -

"Chase me if you can!"

"Illya! Wait up!"

Shirou was chasing Illya in the backyard while I watched them.

"Ritsuka! Come join us." Illya called me.

"I'm okay being in here. I'll just watch you guys."

"Aww, no fair!" She pouts.

" I'm fine."

"Okay!"

She continued to play with Shirou. Then Shielder (Romani) came beside me.

"Ma-Ritsuka are you okay?"

"I'm fine. I was just happy that both of my siblings are all right."

"Indeed."

"Are they playing again?"

Kiritsugu came with Sella and Leysritt. Sella and Leysritt were wearing their outfit from Fate Kaleid.

"Yeah."

"Ritsuka."

"Hmm?"

"Thank you for everything."

"It's no problem at all."

Kiritsugu smiled.

"I will be gone soon. Please take care the both of them."

"Right."

'I'm sorry I couldn't tell you that I can also save you, but the timeline will change drastically. I already made major changes, and that is I saved Illya from the Einzberns and manipulated her magic circuits to extend her life span.'

"I'm baaaaaaack!" Fuji-nee came to visit again.

"Hi, Fuji-nee."

"Look what I got!"

"A camera?"

"Yup!"

"Oh, it's Tiger!" Illya saw her and shouted her nickname.

"It's Fuji-nee!" She shouted, and Illya giggled.

"Enough of that. Let's take a picture."

"That's a good idea," Shirou replied.

"I know, right?"

Fuji-nee looked at the two homunculi.

"You should join us too."

"I don't want-"

"Okay."

Sella was about to decline, but Leysritt cut off her and took her arm.

"What?"

"Daddy, carry me!"

"All right."

"Miss Fujimura, I would like to be the one to take the picture," Shielder asked Fuji-nee.

"Eh? You don't want to be in it, Romani-san?"

"Forgive me. I am uncomfortable with cameras."

'Liar.'

"Oh, okay. Here I'll teach you how."

Fuji-nee taught him how to use it. He was a fast learner.

"All right, everyone, I will take it now."

"""Okay!"""

"I'll join too!"

Fuji-nee shouted and ran towards the group. I was still sitting while watching them. The sight of them felt satisfying at the same time. I was sad.

'It's not complete. I wished that Irisviel was here. I want to revive her, but that's impossible. There is no way I could do that. I'm sorry, Illya, Kiritsugu, that I couldn't save her, but I am happy that you both reunited.'

I lowered my head.

'I'm not even supposed to be here, but you're all happy and safe as long. I will be satisfied. '

"Ritsuka! Come on. We're taking the photo now!"

Shirou called out to me and came back to my senses. I looked in their direction again.

"Huh?"

"Come on! Hurry up!" Shirou shouted again.

"Ritsuka, hayaku hayaku! We're waiting." Illya shouted as well.

"Come on, Ritsuka-chan! We won't start without you!" Fuji-nee called out to me as well.

'Is it all right?'

"Ritsuka! Come on." Shirou called me again, but he approached and offered his hand to me this time.

I stared at him for a second and took his hand. We ran toward the group and went to our positions.

"Okay, on the count of three," Shielder said.

I smiled so brightly while holding my brother's hand.

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1

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2

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3

*Click*

Shielder took the photo. Then the picture came out.

"Let me see, let me see!" Illya came down from Kiritsugu's arms and ran towards Shielder.

"Wait up!" Fuji-nee approached him as well. Then the rest of the group came too as well. Shielder handed over the photo to Illya.

"Wow! It's beautiful!"Illya commented.

"Your right." Shirou agreed.

"Hmm... It's good." Kiritsugu complimented.

"Sella looked angry," Leysritt commented Sella.

"That's just how I look! Coming from you, your face looked blank!" Sella shouted at her.

"The photo went out good. Good job, Romani!" Fuji-nee complimented Shielder.

"Thank you."

"Ritsuka, look!"

Illya showed me the picture. It went out beautifully, just like they said, but as I looked closely, I think I saw a faint image of Irisviel smiling, holding my shoulders while looking at the camera.

"Huh?"

I rubbed my eyes and looked at the photo again. Now Irisviel wasn't there anymore. I was confused that I saw her until I heard a voice.

"Thank you."

I gasped. This time I heard Irisviel's voice. I look around, but she's still not there. I smiled to myself that she thanked me.

'I promise I'll protect them.'