Mikari-chan's glow up

Illyasviel is a homonculi, she's like a doll. Unfortunately because of that, her body will stop growing after a certain time. She will be stuck in the body of a child. 

"Raphael, did you analyze Illyasviel?"

[Answering, Yes. I analysed her. Her vessel is a product of magic technology.]

"Then it's possible to change her vessel into a better one? One that can actually grow up." 

[Affirmative. Would you like me to construct a blueprint for a modified vessel?]

"Oh, yes. Do that."

[Initiating blueprint creation...]

Hmm, I also need to arrange material for creating her vessel. 

Ah well, I'll arrange them when the blueprint is ready.

-------

Next day, I checked the blueprint prepared by Raphael. 

"Hmm, that looks unexpectedly easy... Are you sure it should be this easy?"

[Answering, Creating a vessel would require delicate control of mana. To be able to create it, you will have to create extremely accurate mana circuits.]

"Delicate control... I don't even have proper control yet." 

[Advice, You can practice creating mana circuits on small pieces of metal scraps. Different structure of mana circuits will result in different effects on the metal. You can also discover useful magecrafts for yourself.]

"Okay...? Well, I guess I gotta take one step at a time."

Practicing is not a problem for me. I wonder how delicate my mana control must be.

"Oh, I also have to meet Mikari-chan today. She did say to meet after a week. I wonder what she wanted to show me that took her a whole week."

I put on my shoes and rushed out of the house. 

Let's go back to the same park where I met her first. She is a cute child, so I guess it shouldn't be a problem to befriend her.

I walked to the convience store that I visited before and bought a pack of cookies.

I walked the same path I did that day, and reached the park. 

As soon as I reached the park, I saw a girl sitting on a swing. After looking at me, she immediately got off the swing and ran towards me.

"I was waiting for you, Izanagi-Senpai." She said with a bright smile.

"Wait... You are... Mikari-chan..?" I dropped the cookies I brought in shock. 

Her hair were tied in twintails, like a tsundere. Her face was beautiful, almost like she was a real goddess. Her pinkish pupils were looking at me as if awaiting my judgement. 

She has completely changed from that boyish bullied kid!! In just one week!? 

"Wow, you look absolutely beautiful!" I complimented her. 

Somehow, it feels like I know her... Who exactly is she... Why do I feel like I know her..?

"Waa...~ I-Izanagi Senpai... I-It's a bit embarrassing if you're so straightforward..." 

She covered her face with her hands and looked down. 

"How did you change so much in a week? You look completely different from before." I was curious. She felt unnaturally familiar.

"Ah! T-That... I actually found a manga and found a character called Lilliel. She looked so beautiful that I wanted to look like her... I wanted to look good for you..." She said the last part so slowly that I wasn't able to hear her.

I wanted to ask her what she said, but my attention was drawn to something else. "Lilliel"... I know that character.

I immediately stopped the time.

"Raphael! What's the meaning of this?! How is it possible?!" 

I finally understood what was actually happening. Tachibana Mikari doesn't belong to this world. She is not a part of UBW nor a part of My dress-up darling.

She is from a whole different world. The world of 2.5d seduction. But how is it possible for three worlds to be merged together when I am only simulating only two worlds?!

[I apologise. There has been a mistake. When two worlds are simulated together, they are merged together to create a new world. But since you switched the simulation into Full-dive, the worlds that were merged together were the original ones. When they were being merged together, some small incomplete worlds also merged in by accident.]

But, the system in only simulating two worlds right now. Now that more worlds are joined in this one, what will happen to the simulation? Is it still valid?

[...]

Hey, what happened? Tell me quickly, what happened?! Is this world still under system's simulation?

[...]

Hmm... I'll take that as a no. Since this is an error, will I be compensated?

[...]

Oh come on, atleast give some answer. 

Wait... Could it be... I am stuck in this world since the simulation was an error...?

Suddenly a creepy voice sounded in my head instead of Raphael's voice.

[Haha! It finally got somewhat exciting..!]

...Shit...