Every participating Master knows that the "Holy Grail" will manifest in the final stages of the Holy Grail War, but they are uncertain of its exact location.

Only the heads of the "Three Families" and the overseers of the Church are aware that the Holy Grail does not manifest on its own. It requires a summoning ritual to be performed at a location with sufficient leylines.

Within the territory of Fuyuki, there are four locations with ample leylines that can serve as potential summoning sites for the Holy Grail.

The most suitable leylines for selection belong to Mount Enzou, which possesses a natural cave system called the "Dragon's Cave." It is here that the Greater Grail, based on Justeaze's Catalyst, is set up as a secret altar known only to the Three Families. For the past 180 years, this has been the optimal location.

Originally, the Tohsaka family, as the providers of the land, had the priority to claim the best leylines as their base. However, the magical energy within Mount Enzou is too overwhelming, making it unsuitable as a living location for nurturing the next generation of magi. As a result, they settled for the second-best leylines, which is their current residence, the Tohsaka Mansion. While it may not be on par with the Greater Grail, it still provides sufficient magical support for the manifestation of the Holy Grail.

The third leylines were initially given to the Matou family when they migrated here. However, it was later discovered that the land's spiritual energy did not align with the family's attributes. Consequently, the Matou residence was moved to a different location, and the original leylines were claimed by the Church, which is where the Fuyuki Church now stands on a hill. Although it is located on the outskirts of Fuyuki City, separated by a river, and distant from Mount Enzou, the leylines there are not inferior to the second leylines.

The fourth leylines did not originally exist in this land. Instead, through magical manipulation and adjustments of the three existing leylines, a subtle variation in the flow of mana accumulated over a hundred years. This resulted in the formation of a focal point, a post-natural leyline. Following subsequent investigations, it was confirmed that this location had sufficient leylines to conduct the ritual. Since the Third Holy Grail War, some individuals have regarded this place as an alternative site. Currently, this location is situated at the center of the emerging residential district of Fuyuki and has a newly built civic center.

Shinji naturally chose Mount Enzou as the location for summoning the Holy Grail, not because of any ranking of first, second, or third, but because it was the only choice.

The second leylines are the base of Tokiomi, which is unsuitable.

The third leylines are the base of an ally of Tokiomi, although the Church currently has no one there. However, with Kirei Kotomine's departure, the location will likely fall into the hands of Tokiomi, making it unsuitable as well.

The fourth leylines originally had lower leylines compared to the other three and were located in a densely populated area. In "Fate/Zero's" final events, Kirei Kotomine chose this location to summon the Holy Grail, resulting in a massive fire that claimed numerous lives, including the biological parents of the protagonist of the Fifth Holy Grail War, Shirou Emiya. Any sane person would not choose this place.

Though Shinji has already taken two lives, his ideals remain untwisted, and his choice from beginning to end has been Mount Enzou, specifically the Ryuudou Temple at the peak of Mount Enzou.

Choosing Ryuudou Temple as the summoning location for the Holy Grail has two additional advantages besides its high spiritual energy:

First, it is rarely visited by people. Ryuudou Temple is not a popular temple, and the monks there lead austere lives. Their numbers are few, and they are not knowledgeable about mysteries. Scáthach was able to hypnotize all the monks in half an hour and gather them in a distant room far from the summoning ritual, preventing them from being affected.

Second, it is easily defensible. The hardness of the floor is not the reason. The claim that it is as hard as the Fuyuki Bridge is just a joke. The floor here is made of ordinary stone and is not particularly hard. The real reason is that powerful barriers surround Ryuudou Temple, extending over the entire Mount Enzou area, with the temple at its center. The barriers are designed to repel spiritual beings, and even Servants can only enter through the main path. If defenses are set up at the mountain gate, it becomes an impregnable fortress.

In fact, in the Fifth Holy Grail War, Caster Medea did just that. She dispatched the irregularly summoned False Assassin, Sasaki Kojirou, to guard the mountain gate. As long as Kojirou remained alive and refused entry, no one could enter Ryuudou Temple.

As night falls, Shinji, Justeaze, Kariya, Lancelot, as well as Maiya and Irisviel, the two captives, gather in a guest room next to the main hall of Ryuudou Temple. Shinji, Kariya, and Justeaze analyze the potential situations that may arise tonight using a map of Fuyuki City.

Justeaze sets up the Holy Grail summoning and mana collection rituals while selectively explaining the circumstances to Irisviel and Maiya.

As Justeaze speaks, Irisviel, who can only move her head, and Maiya are filled with unprecedented panic.

The Matou family has two Masters, each with a Servant. One is the enigmatic Scáthach, and the other is Berserker, whose combat ability is mistakenly evaluated to be on par with Archer.

Justeaze has not completely disappeared and has been lurking around, watching their every move.

The Master of Assassin, whom Justeaze is contracted, is a true monster.

He is very familiar with Kiritsugu Emiya and Saber, almost predicting all the actions they might take.

He knows the effect of "Avalon's" true name release, information that neither Irisviel nor Kiritsugu Emiya is aware of.

He knows about Kiritsugu's unique magic, "Innate Time Control," and understands the principles and effects of "Origin Bullets," making preparations in advance to counter them.

He also knows Archer's true trump card and has devised a plan based on Archer's character weaknesses.

He has set a big trap, waiting for the other three pairs of Masters and Servants to walk right into it.

What makes Irisviel and Maiya feel even more desperate and incredulous is that the Holy Grail, which Kiritsugu relies on to achieve miracles and fulfill his wishes, has already been corrupted. The only way to achieve their desires is through destruction. If Kiritsugu were to truly make a wish to eliminate all wars, humanity would face a great disaster—without humans, there would be no wars.

If someone else said these words, Irisviel and Maiya would not believe them, but the one saying it is the creator and core of the Great Holy Grail system, so they cannot help but believe.

The two of them desperately plead with Justeaze to relay this message to Kiritsugu, but they are stopped by Shinji.

The reason is simple:

"Kiritsugu's character, to put it nicely, is resolute, but to put it bluntly, he is stubborn. He won't stop until he understands the true nature of the Holy Grail. With Kiritsugu Emiya's abilities, it's only a matter of time before he arrives here. At that time, he will experience the true nature of the Holy Grail firsthand. Whether Kiritsugu Emiya will collapse due to the shattering of his dream will depend on whether you two can hold onto his heart."

"I can only rely on Maiya because, by that time, I will already..." Irisviel's expression becomes gloomy.

"You won't die." Justeaze gently placed a hand on Irisviel's forehead. "You will survive, just like me. You'll continue to live with your husband and daughter, watching your daughter grow up. And you'll tell your husband those words."

"Lady Justeaze, are you suggesting..." The sudden turn of events left Irisviel almost unable to believe her ears.

"Call me 'sister'," Justeaze emphasized once again.

"Lady Ju... sister..."

"That's right. Let your sister give you a welcome gift."

A brilliant and sacred light illuminated the entire room. It was a miracle surpassing magecraft, the radiance of the Third Magic.

P.S.: Irisviel and Maiya will be safest under Scáthach's watchful eye. Even if they were to learn this information, it wouldn't cause any ripples.

P.S.2: The Holy Grail can't destroy humanity because the guardians of Alaya would eliminate that possibility before it even begins. Please refer to the collaboration event between "Fate/Grand Order" and "Fate/Zero," where Kirei Kotomine emerges from the Holy Grail, and Kiritsugu, who has become a guardian, waits outside to destroy it.