Shinji Matou at Your Service

The principle behind the undying nature is unclear. The related setting material of Tsukihime only briefly touches on it without giving a detailed explanation. What is known is that Ciel is a descendant of Roa (who had descendants before becoming a vampire). The fact that Roa possessed the body of a direct descendant caused an error in the world's order—an uncorrectable error, a bug in simple terms.

This bug causes Ciel to be protected by the world itself, with the world's order permanently freezing her body at the moment Roa awakens within her.

No matter what happens or how her body is damaged, the world's order will restore her body to its frozen state within a very short time.

As long as the source of the bug, Roa, isn't dead, or the world's order itself doesn't collapse, Ciel will remain in this state forever.

She won't grow, won't age, and won't change. It's even more absolute than Scathach, who remains forever seventeen (a joke). Ciel, however, will forever be sixteen (and that's true).

Of course, the only thing the world has granted Ciel is her unparalleled immortality. If this were an ordinary person, it wouldn't mean much. So what if you can't kill them? An ant that can't be squashed still poses no threat to an elephant, and this world is never short of elephants. Dead Apostles, Servants, powerful magi, and various inheritors of mysteries across the globe can easily crush an ordinary person like an ant.

Take Shinji, for example. Killing ordinary people is easy; slashing through a hundred, even a thousand, wouldn't be too hard, and even ten thousand wouldn't be too much effort.

Fortunately, Ciel herself is extremely gifted. Although born in an ordinary family, her potential rivals that of the original Roa. When Roa possessed her, her potential was fully awakened and then frozen by the world, forming the strong foundation of her current abilities.

She possesses superhuman physical abilities, with a magic circuit a hundred times that of a normal magus. In terms of raw potential, she is among the very best of her generation, with only Lorelei as a peer.

However, the gap in their magical abilities is vast.

This gap isn't due to background or environment; it's entirely due to Ciel's resistance.

Human memory is a strange thing, stored both in the soul and imprinted in the brain. Although Roa didn't awaken for long, his memories were fully imprinted in Ciel's brain.

Before becoming a vampire, Roa was an extremely powerful magus and the founder of the Burial Agency. He was often invited to the Millennium Castle, the true ancestors' stronghold, which shows his formidable strength.

After becoming a vampire, Roa reincarnated eighteen times. Except for Ciel (the sixteenth reincarnation, which was an accident—the previous vessel died before he could choose the next one, and by chance, he reincarnated in Ciel, causing the bug), and the unknown eighteenth reincarnation, every reincarnation was carefully selected—no poor backgrounds, no weak potentials, and preferably some non-human blood.

Over these eight hundred years of continuous reincarnation, Roa accumulated a vast amount of knowledge and secret arts, rivaling the two thousand years of the Barthomeloi family's heritage. It's worth noting that inherited knowledge can be lost, and magic crests can fail, but Roa, having evolved into a high-dimensional spiritual entity with the help of Arcueid's power, would not lose this knowledge.

All this knowledge is stored in Ciel's mind, and available for her to access. If she fully assimilated this knowledge, she would be no weaker than Lorelei. However, this knowledge is tied to the painful memories of the destruction of her hometown and the slaughter of her family and friends. Revisiting this knowledge means reliving that unbearable past.

Thus, Ciel has always resisted using magecraft, only occasionally using small-scale spells for convenience in missions, such as suggesting or adding special effects to her Black Keys.

This is one of the reasons why Shinji didn't use his Noble Phantasms and only planned to deal with Ciel using firearms.

The other reason is the Seventh Holy Scripture's weapon form.

As holy light flowed, the scripture was released from its ancient book form, transforming into something resembling a massive shotgun or impact drill.

The entire weapon was over 1.5 meters long, with the widest part of the gun being over 50 centimeters. Its imposing design, with a silver-black metallic shell darker than her deep blue habit, carried a steampunk aesthetic. The sudden shift from a medieval-style book to a modern weapon provided a strong visual impact.

That's right—you didn't misread it—this is the Holy Scripture passed down through the Church for millennia.

Of course, it wasn't originally designed in this form. The Seventh Holy Scripture was initially used for its sacred symbolism, as a tool for the final sealing rites. Later, it gradually evolved into a weapon.

The earliest weapon forms were spears or stakes, and as time progressed, it integrated more modern weapon characteristics, becoming a gun-sword hybrid suited for combat. Up until this stage, the scripture still retained some of its sacred dignity.

The steampunk-style impact drill is Ciel's modification, inspired by her preferences. When Shinji first saw Ciel pull out this weapon in a past life while playing a game, he was utterly shocked. It felt like suddenly encountering a modern tank on the medieval battlefield of Mount & Blade—a truly surreal experience.

Now, however—

"Great weapon. I like it. I have something to show you as well."

Admiring the scripture, Shinji took advantage of the brief moment before it fully stabilized to pull out two, even more, imposing weapons from his backpack (or coffin).

A rocket launcher and a six-barrel Gatling gun—Ciel was so startled that she nearly dropped her impact drill, and even Caren's eyes widened in disbelief. Even Merem showed a notable level of surprise.

The rocket launcher and Gatling gun themselves weren't the issue; they'd seen modern weapons before and had even faced off against them during missions.

The Church, unlike the Mage's Association, wasn't opposed to technological advancements. It was common knowledge that many Executors actively requested partial cybernetic modifications to better complete their missions of hunting heretics.

The problem was how Shinji pulled out these weapons. Everyone could see his backpack—it was only so big. Fitting a flamethrower might have been possible, and cramming in some grenades and blood packs wouldn't have been too hard, but where did these weapons, which were much longer than the backpack, come from?

This wasn't some mystic weapon with shape-changing abilities that could ignore the rules of physics.

Could it be that the backpack was a rare space-type artifact? Just how many weapons were hidden inside?

Shinji was pleased with their reactions. Grinning with a Gatling gun in one hand and a rocket launcher in the other, he said:

"Come on, let's hurt each other!"