Shinji Matou at Your Service

Kirei Kotomine's daughter, Caren, had known about him since she was very young.

Although Kirei had abandoned his daughter, he continued to send child support to the priest who had adopted Caren. Kirei, who lacked normal human emotions and had even contemplated suicide, believed that his daughter would only suffer if she stayed with him, so he entrusted her to the church for adoption. However, he did not neglect his duties, which is how Caren learned about her father's existence and name.

Having never met her father from the time she could remember, and sharing a similar emotional void, Caren's feelings toward Kirei were extremely indifferent. She neither liked nor disliked him; at most, she was curious about what her only blood relative looked like and why he was imprisoned there.

Caren took advantage of a meal delivery to meet Kirei.

The moment she saw him, Caren knew that this was her father because their eyes were too similar.

Likewise, Kirei recognized Caren. Her appearance was just like his late wife, Claudia—quiet, detached, and reminiscent of a hydrangea in spring.

They shared many similarities: a blood connection, a fractured mind, and similar circumstances. Normally, this should have led to a sense of resonance, a heartwarming reunion between father and daughter, and a story of healing.

However, fate played a cruel joke on everyone once again.

Before they could exchange a single word, Kirei went mad. With strength that no human should possess, he shattered his restraints and blasted open the door to his cell.

Caren, standing outside the cell, was caught in the explosion, severely injured, and lost consciousness.

When she awoke, the deepest parts of the Cistercian monastery were destroyed, with many monks dead or injured, and several ancient buildings damaged—all caused by Kirei.

Unlike last time, when the Knights helped to suppress him, this time, Kirei escaped with no one able to stop him, committing heinous crimes before vanishing without a trace.

Afterward, the Knights conducted an investigation and concluded that Kirei was solely responsible and that Caren was not to blame. However, Caren stubbornly believed it was her fault—that she had somehow triggered her father's madness and was the cause of everything.

Her reasoning was simple.

Why did Kirei go mad precisely when she delivered his meal and not before or after? Why was she the first to see him lose control and yet only suffer injuries instead of dying? Why, when she saw the devastation in the monastery, did she feel such overwhelming anger? She had never cared about the place or the people before.

Anger, anger, anger.

For the first time, her empty heart was filled with something—an overwhelming darkness that strangely brought her joy and pleasure. But that pleasure was sinful, a perverse delight against reason.

Caren realized she was the daughter of a sinner and that she, too, had been tainted by his sins.

What could have driven someone destined to be a saint to become a sinner? What had awakened the darkness within him and herself?

The answer could only be a demon.

He was possessed by a demon, which drove him mad. And because of her Masochistic Spiritualist Constitution, she was similarly influenced by the demon.

It was the demon. It was the demon. It was the demon.

For the first time in her life, Caren made a decision based on her emotions. She submitted a request to the Church to undergo the most rigorous combat training, to hunt down her father, to exorcise the demon that had possessed him, and to atone for his sins.

Of course, that was just the surface reason. Beyond that, she yearned for the feeling of being emotionally fulfilled.

The more unattainable something is, the more it is desired. Just as Fujino sought pain because she couldn't feel it, Caren occasionally found joy in pain even after regaining her sense of it. Despite the darkness and sinfulness of this desire, Caren instinctively pursued it.

Given the previous conclusion that Kirei was possessed by a demon and that Caren was a Masochistic Spiritualist Constitution with a radar for detecting demons, the Church eventually agreed to her request after much deliberation, transferring her from the Cistercian monastery to the Executors' training camp.

As the daughter of Kirei Kotomine, Caren was highly talented. Her small body harbored great potential and driven by the emotions of anger and pleasure, she trained day and night, pushing herself to the brink of self-destruction. She quickly graduated from the camp and successfully became an Executor.

However, being an Executor was not enough. Caren had studied her father's career and knew that he was one of the Church's top Executors, powerful and highly accomplished. He was far beyond her current abilities. Worse still, those possessed by demons may go mad, but they also gain great power, widening the gap between them.

To defeat Kirei, she needed more, greater power. Normally, this would require either rare treasures or time to accumulate strength. The Church had treasures but wouldn't give them to a novice Executor without reason, and Caren lacked the confidence to grow quickly on her own, especially after learning that the Church had sent Riesbyfe Stridberg and herVestel Shield Knights to hunt down Kirei.

Riesbyfe was the Church's elite, a rising star with knights under her command who were as strong as Executors. This put immense pressure on Caren.

During her training, Caren's anger only deepened, growing more intense as if to compensate for the emptiness of her previous life, twisting her from indifference to the opposite extreme.

Caren knew she had gone mad.

What was more frightening was that she didn't mind it. Perhaps her fugitive father felt the same, letting madness take over in pursuit of inner fulfillment.

When she learned that another candidate for the Burial Agency had been killed and a new one was needed, Caren, driven by madness, made a shocking decision. Despite opposition, she volunteered to become a candidate.

Ciel, who oversaw the initial selection, initially refused her application and returned it, but Caren persisted. Eventually, she succeeded in persuading Ciel with the reasons of revenge and atonement—the same reasons that had led Ciel to join the Burial Agency.

After passing the initial selection, Caren cleared several more stages, and even Narbareck's interrogation didn't shake her resolve. After all, the Burial Agency was known to drive sane people mad, and a person who was already insane couldn't be pushed any further—unless the pressure reversed the madness.

In the end, Caren became a candidate for the Burial Agency, enduring longer than most and gaining great power and achievements.

It's rumored that Narbareck is considering breaking tradition to create a new seat—the Eighth Seat for the Demon Nun.

PS: Well, somehow Kirie changed the fate of Caren saving her from being tainted by demons. All Fallen girls except for Kohaku are still virgins.