Ascendance of a Bookworm X-Over, Nasuverse Style!

Shirou becomes Main

Shirou died peacefully at the age of 25. Merely four years after Clock Tower.

He did not live long in his puppet body Rin was furious she felt Touko cheated her out of the deal when she paid good money and assets using the Matou assets with Sakura's blessing and yet...!

Sakura, desperate, poured as much mana as she could to keep him alive but it was futile.

'Hey...its enough.' said Shirou weakly with a sad smile. 'I think despite everything, my soul is too damaged by my Reality Marble. Magecraft or Sorcery can't heal souls.'

That was reality as it would take a god-like power to do such a thing.

Sakura was trying to deny reality and still kept trying as he was her reason to live.

'Tohsaka...is my old body still around?' Shirou asked.

'Y-yeah, what of it?' Rin sputtered, 'Even after all these years it wouldn't rot like any corpse would and I can't figure why!'

'My body has Avalon, Saber's sheath and Noble Phantasm. Its useless now as it only works when Saber's around but it might be useful to you two someday. It saved my life during that Fuyuki Fire and I always healed quick since.' several jaws dropped. 'But since the battle in the cave...its empty now. And having that thing in me since the big fire...its why I'm the way I am now. I just realized that when I'm about to die.'

'Rider!' Sakura cried as Rider quickly left to do the unsaid order, retrieving Shirou's body from Rin's workshop. It was as tattered as ever...with blades even if Rin cleaned it up. A gruesome sight, Rider thought. But it all makes sense as his Origin was Sword which made his Reality Marble possible.

And a sheath's origin is a sword as sheaths are created to safely put away a sword when not in use.

Upon giving the body to the sisters, Rin extracted Avalon and studied it. But she felt it.

It still has power. In fact, plenty of power.

'...you moron, it still has mana! By the loads!' Rin cried, 'You were near Saber when you fought her in the cave, replenishing it's mana! How can you not know?!'

'Well, it stopped working when I fought Kotomine after...so I thought...' came the sheepish reasoning.

'Or maybe it's because of Angra Mainyu, neesan.' Sakura said softly. 'With the Grail as back-up, it stopped the flow to senpai when I changed Saber so he too, has control over her somehow, particularly her power...and with his Reality Marble consuming him...he...' she choked in a pained voice.

'Talk about petty but considering we screwed him over by saving you, it just had to have the last laugh.' Rin shook his head. 'It's his fault Sakura, not ours but Illya kicked him out of our world for good.' she scowled. 'But now, how do you feel, Emiya-kun?' Rin asked him. 'Any better?'

Shirou shook his head.

'Oh...' Rin deflated.

'Its alright...while I still have time...go call Fuji-nee. Her family lawyer's the one who drew up dad's will leaving all he's got to me so...I'll leave all I got to Sakura since you sold everything the Matou owns Sakura now lives here, might as well make it permanent.' said Shirou with a smile. 'I promised Sakura I'd make her happy but in the end, I made her cry again.' he said, utterly sorry for it. 'All I ever gave her in the end was cooking, and this place.'

'Senpai!' Sakura cried.

He gave her more than that.

He gave her hope and a reason to live.

But those were two things he wouldn't understand and unable to comprehend due to what he was even if he was so kind and gentle. As a sword, he could only act rationally in order to be of use, to have a purpose. More rationally than a magus it was good that his father, the late Magus Killer taught him all that's morally good and just that he acts on it. That he acts for what's best for people around him. For Rin, he was a reliable friend. For Sakura, he tried his best to be a lover...

Her sister felt that if a magus raised him...good lord.

Shirou, after Rin did some tweaking on the Fujimuras, was able to write his will, making them believe he was terminally ill with Cancer and it was too late when they noticed his symptoms.

And he died a week after writing his Will.

But why?

WHY is it that he woke up, hearing a little girl's sobbing voice, saying, 'It's hot...it hurts...I can't stand this any more...help me...'

She was in pain, but he saw it.

A beautiful girl with blue hair, but she's clearly poor and filthy. Living in a shack. She was ill with some sickness she died just now and her soul left her body...and he was shoved in it.

He felt it too.

He was reborn anew through this method.

He received this girl's, Main's memories. He is now her.

The real Main passed away due to Magical Consumption. Because poor people don't get any education, they're clueless about many things, especially if born with magic.

Mana pools up to overflowing, gradually harming the body yet forcefully healing it at the same time while causing intense stress and overcompensating that growth was compromised.

For a poor, malnourished child from a poor family, and living in a filthy house and clearly never bathed all her life and so did her family...it was no wonder she died and he was now reborn as her. He also inherited her immense powers, changing his soul too. This girl is one hell of a magus, and nobody damn knows.

Changing his soul aside, it healed him too, but his Reality Marble lost forever. He was no longer a Sword...but now an immense Void. A non-elemental power that enables him to learn anything he can think of as Void is basically a power that's a blank slate similar to Ether that it can be shaped into anything you want. You can use it to fuel any spell you made and cast. But to use elements, you need something pre-existing beforehand, like a torch for fire, or nearby water to manipulate and boost en masse by creating more of it through a medium.

He lucked out but this seems to be a peaceful world...

...he also regained what he had long lost.

...a heart.

Main, poor girl, unwittingly gave him her body, her power and now, her heart, enabling him to feel what he never has before.

Emotions.

And his past hit him like a ton of bricks, making him realize how empty he was all this time, because he was a Sword.

He exasperated and troubled many people in his wake, and failed to give Sakura what she truly wanted. It was his regret.

"Main-chan...thank you..." he thought. "Dad...Fuji-nee...Otoko-nee...Issei...Sakura...Saber...Tohsaka...Illya...Lord El-Melloi II...I'm sorry I was a heartless idiot. I troubled everyone and now, even as Main, I'll be troubling my new family too. Gotta do something about that."

Shirou discarded his heartless self that only caused exasperated grief to those around him, and would accept his new identity as Main.

Gotta get used to being a girl from now on.

He err SHE could fully use this body with no trouble. Just that, she felt she has the worst fever and weakness in history. "Yeouch...what I feel now about Magical Consumption...damn books can't do this justice! This is a lot of fuckton worse!" she cringed as she felt so...

...miserable.

"I'll have to adjust too. I mean, I got a new family but this time, I'm not an orphan." Main smiled.

In this life, she has doting parents, and an older sister willing to do anything for her because she was always weak and easily gets sick.

In short: USELESS.

"...being a burden was never my schtick. Its not my style at all." Main frowned.

She expelled a lot of mana in her body and healed her fever effortlessly using Healing Magecraft.

Heh, just because he's a 'Cursed Specialist' to quote the lone survivor of the Fourth, doesn't mean she won't crack books! And crack books she did, devouring libraries when school let out while Rin works under Zelretch who took her in as his heir to Kaleidoscope for successfully completing his homework where generations before her failed.

Due to Avalon's nature for many years within her as Shirou, she gained an incredible talent in Healing, Barriers and Bounded Fields. Her talent was First-Rate in it that she surpassed most people in Clock Tower, even the freaking Lords despite her pitiful circuits. She was basically the best doctor by the time she graduated Clock Tower, all the while in a puppet body but she had to be reliant on Mana Generators to back her up when fixing people who screwed up in their experiments. The only thing she can't do was if they messed up even beyond her ability.

She left Sakura her research so she would become her successor to her Healing Craft she herself designed to give her a great career as a Magus while Rin already has a career. Rin also 'took back Sakura' that she's a Tohsaka once more and they will now work in restoring their house that Rin irately said 'Kirei mishandled!' to her irritation.

Her family used the Feudal System with them owning all of Fuyuki, and everyone paying rent to them that its basically raining money on them every year. Not as rich as the Edelfelts though, if Luvia could own jewels the size of medicine balls she could use at least, twenty times before they turn to ash while Rin's thumb-sized jewels immediately goes poof after use, though she can store mana in it for years.

(seeing those jewels made Rin seethe in jealousy and got her angrier at Kotomine all the more)

Something like consuming was barely an effort for her, especially with her new powers.

Once she got up, she looked at herself.

And sweatdropped.

'...I'm like an infant...' she choked out. 'Gotta do something about it too. Main's five years old but this height is just...demeaning.' she cried waterfall tears.

She then looked around and scowled.

"...what a mess. And why is Tuuli-chan not sick yet?!"

As much as Main wants to clean this room, she has to know about her family's attitude about magic first, so...

...manual cleaning it is. Sigh...

The floor is so sandy and grimy...uggh...

'Yosh, I now know where to work on. This is so inhumane...how on earth did they live like this?' she croaked out as her new mom came in.

'Main! You're OK now?' she asked worriedly.

'Yup, I'm OK now mama.' "Gotta get used to that..." Main smiled. 'But I feel icky.'

'You usually do.' her mother, Eifa chuckled. 'Hungry?'

'Mm.'

That was another thing Main intends to deal with.

Food here sucks. Bland and tasteless. Just flavored with vinegar and salt. Yuck.

xxx

Her mother picked her up and took her to the kitchen, like a baby.

Setting her down on the chair, if Main can even call it that, Eifa took out some bread for her as well as some broth.

Main tasted the bread. "...its like Rye bread, kinda good or is this actually Rye?" Structural Analysis...hmm...its taste and texture is similar to Rye, but its nutrition is great for the eyes! This bread alone can make eyes happy for a whole day that eyesight will never deteriorate. Moreover if a pregnant lady kept eating this until childbirth, their child is guaranteed to have sharp eyesight at birth.

And this bread, is effing cheap. However, its dark color and texture is no doubt, unappealing to the wealthy's sense of beauty they feel they deserve, so they labeled it as 'poor people's food'. Typical. At least poor folk get some nutrition...

As for the broth...

...she whimpered.

Its just soggy veggies in salty-sour flavor. Ick...

Structural Analysis on veggies used...

...what the hell?

If those sisters died and are reborn here like he was, Rin would probably enjoy this.

The food here...is magical.

So now Main has a goal.

To bring this world out of dietary dark ages!