Crossover: With Heaven-Defying Insight, I'm Shaking the Very Aeons

In Germany, within a forest rarely trodden by man, lies a mysterious ancient castle with a history of over a thousand years.

Einzbern Castle.

As one of Fuyuki City's Three Founding Families, the Einzbern family's main base of operations was not in Fuyuki, but within this ancient castle.

In terms of long-standing heritage, status in the magus world, and the wealth of their worldly assets, the Einzbern family actually far surpassed the other two. The very foundation of the Holy Grail War ritual was laid by them.

They also owned their own castle in the suburbs of Fuyuki City.

For every Holy Grail War, the Einzbern family would dispatch their chosen Master to Fuyuki to participate. To master the Third Magic, Heaven's Feel, through the Holy Grail War ritual—this had been the Einzbern family's greatest wish for hundreds of years.

Now, although there was still about a year until the war officially began, the Einzbern family had, as always, made preparations in advance.

At this moment, in the center of the castle, the patriarch of the Einzbern family, Jubstacheit von Einzbern, stood in the middle of the main hall with a solemn expression.

On the table before him rested an extremely mysterious box.

In front of the table, a silver-haired, red-eyed girl who looked to be about seventeen or eighteen, with a naive and innocent expression, was curiously examining the box.

"Irisviel!"

The solemn old man called out the girl's name.

"Yes, Grandfather."

The girl immediately retracted her gaze and adopted a serious attitude, though her eyes clearly still lingered on the mysterious box.

"For this Holy Grail War, we have fully learned our lesson from the last time. We absolutely cannot summon another useless Servant like that."

The old man ignored her expression and spoke directly. As a participant in the Third Holy Grail War and the former Master of All the World's Evils, Angra Mainyu, he felt deeply about this mistake.

To put it bluntly, the Heroic Spirit he had summoned might not have even been able to beat him, the Master.

Having learned from this painful experience, he reformed his family's strategy.

"To this end, I have spent a great deal of money to purchase a very special catalyst. If we use this to summon, even the worst possible outcome will guarantee us a first-rate Servant."

In the Servant summoning ritual, the catalyst had a very high influence on the summoning result. As long as the Heroic Spirits associated with the catalyst were all powerful individuals above a certain standard, it could guarantee a baseline level of combat strength.

However, catalysts that could meet such requirements were truly few and far between.

"What catalyst is so amazing?" Irisviel blinked, asking with great curiosity.

"This is Avalon, a catalyst just unearthed from Cornwall."

Without any intention of keeping her in suspense, Jubstacheit directly opened the lid, revealing the incredibly magnificent scabbard within.

"Avalon? Isn't that King Arthur's scabbard?"

Irisviel, who was very knowledgeable about Celtic mythology, reacted quickly. King Arthur's fame was not low anywhere in the world, and it was especially high in Europe.

Even she, a homunculus, couldn't help but have her eyes light up upon hearing this news.

"Doesn't that mean that for this summoning, we might be able to directly summon the legendary King of Knights?"

Aside from the ridiculously overpowered individuals in the myths, a Servant on the level of the King of Knights could be said to be the top tier among normal Servants.

If placed in past Holy Grail Wars, she could pretty much steamroll the competition.

"Even if it's not King Arthur, the other Knights of the Round Table are also first-rate Servants."

Jubstacheit was clearly very confident in his decision this time.

"As the Lesser Grail, your ability to supply magical energy is already first-rate. As long as you cooperate well, this Holy Grail War will surely be our victory."

"To fulfill the long-cherished wish of the Einzbern family, Irisviel, this Holy Grail War is all up to you!"

In addition to fixing the bug where the summoned Servant might be too weak, he had also fixed the bug where the Lesser Grail was easily broken, by having Irisviel herself bear its function.

Therefore, there was no need to worry about the supply of magical energy.

With so many improvements, he felt that this time, their side was bound to win.

"Yes, Grandfather!"

Despite knowing that this order was sending her to her death, Irisviel, being a homunculus, did not hesitate in the slightest. She was born for the victory of the Holy Grail War; death held no particular fear for her.

Seeing Irisviel's declaration, Jubstacheit nodded.

"Then take this scabbard and begin the summoning ritual! Besides summoning a Servant, it can also ensure your body functions normally before the Great Holy Grail appears, placing our side in an invincible position!"

Saying so, he reached for the box.

And then, his hand met empty air.

"?"

Jubstacheit froze for a moment, looking down at the empty box before him. The box itself was fine, but what about what was inside?

"Where's the scabbard?"

Unable to determine what had happened, he immediately looked at Irisviel. Of course, he didn't suspect her of taking it. Setting aside whether there was a need to, Irisviel simply didn't have the power. He just wanted any possible information.

On this point, Irisviel, who had been focused on the magnificent scabbard the whole time, did indeed have something to say.

She described it with a dazed expression.

"Grandfather, I just saw the scabbard go shoom and disappear."

"Spatial magecraft used within the castle's bounded field?"

Jubstacheit's expression changed instantly.

"All units on alert! All homunculi, deploy! Search for the intruder!"

Without a moment's hesitation, he immediately issued the order.

The entire castle suddenly burst into activity. All sorts of detection spells were activated, but they couldn't find even a shadow of an intruder. If the thief was some great magus skilled in spatial arts, they would have likely already vanished into thin air.

Of course, there was an even more terrifying possibility: that the other party hadn't even come in person, but had simply cast a spatial transfer spell from a distance. However, this scenario was generally not considered.

Apart from the Second Magician, Zelretch, no one else had developed spatial magecraft to such a degree. It couldn't be that a god had descended to the mortal realm, could it?

Seeing that the search was fruitless, Irisviel didn't feel too much regret. Although she was curious about the thief who could steal something from right under her grandfather's nose, there was a more important matter at hand.

Looking at the already prepared Servant summoning circle, she asked with a pure expression, "Grandfather, the catalyst is gone. What do we do about the Servant summoning now?"

"..."

Jubstacheit finally felt a deep sense of exhaustion. Catalysts were extremely precious items even in the magus world, and those connected to famous Servants were even more so. They weren't something you could just buy off a shelf.

If it had been stolen a few years ago, he would have had time to prepare a second one. But at this point in time, it was too late to do anything.

If the person who stole the catalyst had just happened to choose this moment, then it was one thing. But if the other party had done it intentionally...

"This Holy Grail War seems to be more dangerous than any before..."

With a deep sigh, Irisviel, as the Master, could only be forced into action, directly performing a compatibility-based summoning.

---||---

On the other side of the planet, in the island nation of the Far East, Fuyuki City.

"I've finally gotten my scabbard back! Thank you, Master!"

Artoria excitedly held the long-lost scabbard, the ahoge on her head standing up in excitement, her eyes full of gratitude as she looked at Su Mo.

"Mm."

After a casual reply, Su Mo turned to look at Rin.

"Is Lord Su Mo leaving?" Rin immediately guessed his intentions.

"Yes, what needed to be done is done. I'll be back when the Holy Grail War begins," Su Mo explained.

"Oh!" Rin nodded, wanting to ask him to stay but unable to find the words.

At this moment, Sakura, who had been silent all this time, suddenly took a step forward, gathered her courage, and tugged on the corner of Su Mo's clothes, stammering.

"Lord Su Mo, I... I can sweep the floor, do the laundry, and cook a little... I can learn whatever else I don't know..."

The little girl, no more than five or six years old, looked up, her eyes full of apprehension.

"So... can you take me in? I eat very little, and I'm not afraid of going hungry."

The little girl tried her best to lower her own value so as not to be a burden. Her only firm desire was to leave with Su Mo.

Hearing this, Artoria was a little stunned, not yet understanding what was happening. Rin, however, froze for a moment before quickly understanding her sister's thoughts.

"Sakura, you don't want to go home—"

She cut herself off mid-sentence. Although the Matou family had been destroyed, her father had personally declared that he had severed ties with Sakura.

Even if she could go back temporarily, it probably wouldn't be long before her father found another adoptive family and sent Sakura away, right?

Since that place was no longer her home, there was no need to go back.

For the current Sakura, there were only two people she could trust. One was her older sister, Rin, and the other was Su Mo, who had saved her from her fate. Her only choice was to hope that Su Mo would take her in, allowing her to get away from her previous family.

Thinking of this, Rin didn't know what to do and could only turn her gaze to Su Mo.

Faced with everyone's stares, Su Mo stated the plan he had already thought of.

"Let me be clear beforehand: I don't have time to take care of you, nor do I need your care for the time being."

Hearing this, Sakura's eyes dimmed, and she hung her head, not intending to pester him.

And then, Su Mo's tone changed.

"However, if you are willing, I can introduce you to a teacher. Her name is Pandora. You can learn magecraft with her... and after you've completed your studies, I can consider letting you become my assistant."

He had already thought of how to place Sakura before coming. As a magus, Sakura possessed the rare Imaginary Numbers attribute, and her talent for magecraft was no less than Rin's. If she grew up, she would be an excellent candidate for either an assistant or a test subject.

And as it happened, he had an idle Earth Mother Goddess, Pandora. Entrusting Sakura to her would not only solve the problem of talent development but also Pandora's personality issues.

Having a disciple to divert her attention would be a good way to alleviate Pandora's fear of loneliness and her overly clingy nature. For Su Mo's research, it was a win-win situation.

"No problem, I can do anything!"

Hearing Su Mo's reply, Sakura immediately lifted her head and readily agreed. In truth, she didn't know who Pandora was or where she would be going. But any place was better than her former home.

What she didn't notice was that upon hearing the conditions Su Mo mentioned, her older sister's jaw dropped, nearly hitting the floor.

"Miss Pandora?" Isn't that a goddess?

Rin's heart pounded with shock. Although she had never met this goddess, she had heard Su Mo introduce this creator of Godslayers before. In other words, if she agreed to Su Mo's conditions, she could become a goddess's disciple?

Where else could you find such a good deal?

"Lord Su Mo... actually, I can do it too!"

After a moment's hesitation, Rin spoke up bashfully.

"Sis?" Hearing this, Sakura was stunned, then turned and took Rin's hand. "Sis, you don't have to do this. You've already done so much for me by bringing Lord Su Mo here. You don't need to keep sacrificing yourself for me. I really don't want to go back to the Tohsaka house."

She thought Rin wanted to switch places with her so she could stay at home. Out of gratitude for her sister and her own aversion to the Tohsaka family, she was naturally unwilling to let Rin sacrifice herself again.

"No, Sakura, you've misunderstood."

Hearing this, Rin gave a wry smile. She wasn't making a sacrifice; this time, she really wanted to go and enjoy the good life with her sister! It was a god-level teacher!

"Sis, don't do anything foolish! Fa... that man still loves you very much, Sis."

Sakura naturally didn't want Rin to run away from home with her. She knew very well that, apart from herself, the Tohsaka family was still a happy family of three.

"Alright..."

Although the misunderstanding wasn't cleared up, Rin didn't insist. After all, she was still young, and her dedication to the path of magecraft wasn't yet strong enough to make her abandon her family.

Having not been abandoned herself, she really couldn't bring herself to give up her parents.

"Then you have to listen to Lord Su Mo, and don't ever hide anything from him, okay?"

In the moment before parting, Rin put on the air of an older sister acting as a mother, constantly reminding her younger sister.

"Mm, I know."

The always-obedient Sakura nodded repeatedly, listening patiently.

Artoria, who knew of the Tohsaka family's affairs, also felt sympathetic toward the little girl before her. She took Sakura's hand and said to Rin, "Don't worry. On my honor as a knight, I will take care of her."

"Mm! Thank you, Lord Su Mo! Thank you, Sister Saber!"

Young Rin gave a deep bow to her two benefactors. When she stood up again, the three figures before her had completely disappeared.

Looking at the Matou residence in the distance, where the flames had already been extinguished, and then at the mountain path beneath her feet, a gust of wind blew past.

The six- or seven-year-old girl suddenly remembered something.

This place was dozens of kilometers from the city. How was she supposed to get back?