Before this chapter begins, I would like to clarify a point with you regarding something . Rule Breaker would have no effect on Devil's pieces ; Medea's Noble Phantasm has powerful conceptual effects on all forms of magecraft, but it has limits to what it can nullify .(Excerpt from the wiki) Ultimate anti-magecraft Noble Phantasm, capable of dispelling and destroying all types of magecraft .A dagger that nullifies all effects created by magecraft, be it an enchantment, a connection formed by contact, or even life created by magical energy. Once it comes into contact with the enchanted object or person, enchantments, contract-bound connections, and creatures created and sustained by magical energy will all be returned to their original components in a state 'before their creation." Contracts will be erased, and those with life will immediately cease to exist. There is a limit to what it can dispel; Noble Phantasm-ranked artifacts will never be returned to their original state, regardless of the rank of the Noble Phantasm in question.

Given the effects of Devil's Pieces , one can argue that they possess at least the rank of a Noble Phantasm, so "Rule Breaker" would not work on them

He stood alone on the Hill of Swords, confronted by the shadow of all the crimes he had committed.

He had never aspired to this future, yet circumstances had inexorably led him in this direction, pursuing an unattainable ideal, and the path he trod inexorably led him towards his own destruction.

He found himself constrained by this singular alternative, that of committing an unthinkable act, for it was the only way to safeguard as many lives as possible.

To end the life of the woman he cherished, as she was the trigger for an unprecedented catastrophe that threatened to engulf countless souls.

The second woman he had loved met her end while protecting her beloved, thus fulfilling the last task entrusted to her by her master, in a final heroic act, even though her legend depicted her as a monster.

His life was marked by Several thousand atrocities committed in the name of the greater good, staining his hands with the blood of innocents. Nevertheless, he never aspired to be celebrated as a hero; all he desired was to save lives, for the sole purpose of experiencing happiness himself.

By the end of his existence, he had sacrificed and lost everything. However, he departed with a pure smile, akin to that of a child.

Yet, his torment continued even beyond death.

.

.

.Shirou abruptly woke up, hastening to escape the dream he had just experienced.

He glanced around, relieved to find himself in his own room. The memory of a stunning woman with long violet hair and glasses lingered in his mind as he slowly snapped out of his stupor.

As he began to regain his full senses, he noticed something unusual. "Why am I naked?" He also observed a strange tattoo on his left hand, which had a red color and a unique shape resembling a sword.

As he leaned on his bed, ready to get up and change, he felt that he was touching something exceptionally soft and plush.

As he was about to turn his head to see what his hand was touching, he heard a soft moan, "Haaaa ."

When he looked to where it came from, the word "surprise" couldn't describe his state at that moment; he had reached a level far beyond mere surprise, gazing at the scene before him in a trance-like state.

In front of him stood a buxom redhead, completely naked and sleeping. He immediately recognized this girl because she was none other than Rias Gremory.

As he was in a state of shock, the redhead woke up, stretching and letting out a soft "Mmmmm." Upon waking, she noticed Shirou's hand pressing against her chest.

At first, a blush appeared on her cheeks, but it was quickly replaced by an inexplicable smile as she noticed Shirou's expression. She said in a slightly sensual voice, "Well, Emiya-kun, I didn't expect you to be so wild in the morning." This only exacerbated the misunderstanding.

The first thought that crossed his mind was, "Damn, she's sexy," despite his experience with women, he had to admit that Rias was by far one of the most beautiful he had ever seen.

However, this was quickly replaced by a multitude of questions that raced through his mind at once: "What's going on? What did I do last night? Why is the heir of the Gremory family in my bed? Is this going to cause me trouble? How did we end up here..."

As he was lost in his thoughts, Rias's voice interrupted him. A slight blush appeared on her cheek as she said, "Could you please let go of my chest?"

Realizing that he still hadn't released his grip on her chest, Shirou prepared to take a step back. However, instead of doing that, he slid forward, losing all his strength and his head falling directly onto her chest. At that moment, it seemed like he had suddenly lost all his strength.

Understanding the situation, Rias continued to speak, "You'd better not push yourself, even though most of your injuries are healed, there are still some left."

Shirou struggled to get up, trying to remember how he had ended up in this situation. Suddenly, fragments of memories from the previous night resurfaced in his mind.

"Wait... but I'm supposed to be dead?!" he asked with confusion, voicing his question aloud.

Faced with his confusion, Rias replied, "Yes, indeed, but I resurrected you."

However, her response was met with something she didn't expect. "Exactly, that's the problem. Normally, not even a devil should have been able to bring me back to life," he said in a way that emphasized his surprise.

Rias looked at Shirou in bewilderment. She had expected anything but this kind of reaction. Normally, someone who was supposed to be dead against their will should be overjoyed to be alive. Why didn't he have that reaction, and why was he so certain that a devil shouldn't have been able to resurrect him? She would have to clarify that at some point, but for now, there were other priorities. After thinking for a moment, Rias decided to discuss the room she had used for the resurrection later, as he seemed too confused at the moment.

Shirou sighed. It wasn't that he wasn't happy to be alive; it was more that it didn't seem normal. He would need to investigate this further. Moreover, he had noticed that he no longer felt his soul being crushed by the Saint Graph , which was likely related to demons being mysterious beings like Heroic Spirits. Now that his soul and the Holy Grail were roughly at the same level in terms of rank, it no longer crushed his soul and body, at least until proven otherwise. He would have to look into it more closely. For now, he could rejoice in being able to see his family again.

However, at that moment, another unanswered question crossed his mind. "How did you end up naked in my bed?" he asked suspiciously.

"Even after you were resurrected, you had many injuries, some of which were infused with the holy attribute. I had to spend a large part of the night healing you, extracting the blades from your body, and then using healing magic while holding you. In the end, I fell asleep in the same bed as you," she explained.

Shirou's face went from surprise to a remorseful expression. "I'm truly sorry you were forced to do that," he apologized sincerely.

Rias simply laughed. "You have no need to apologize; I did it of my own accord," she said.

As she moved closer and gently lifted Shirou's chin, which had remained lowered in apology, Rias repeated in a soft voice, "Furthermore, what kind of master would I be if I let my new knight die?" with a smile.

As they both started to get up to dress, Shirou suddenly had a bad feeling. At that very moment, the door to his room opened, and the gentle voice of Irisviel echoed.

"Shirou."

Upon hearing his mother's voice, he hastily grabbed the blanket and covered Rias, but it was already too late as she had opened the door with a breakfast tray in hand.

"Since you woke up so late, I brought you breakfast in bed," she said.

The first thing she saw was Shirou and a completely naked girl. Upon seeing the scene before her, she did one thing, with the motherly smile only she possessed: "Shirou."

Shirou rushed to correct her, "Mom, it's not what you think."

His voice betrayed a certain underlying joy, and she replied, "You should have told me you were inviting your girlfriend over."

.

.

.

After lengthy explanations aimed at dispelling the misunderstanding, Shirou eventually gave up on trying to explain anything to Irisviel, who seemed determined to believe that Rias was his girlfriend, which seemed to amuse the devill.

He had to leave for school, and Illya and Chloe appeared to be sulking about the situation. Before he left, he took care to wrap the tattoo with a bandage.

As they walked towards the high school, accompanied by Rias, Shirou could hear various conversations among the students:

"I can't believe Emiya and Gremory are walking to school together!"

"Do you think they're dating?"

"DAMN, WHAT A LUCKY GUY!"

There were different reactions: curiosity, anger, and those who were drawing their own conclusions.

Throughout the journey, neither Shirou nor Rias spoke to each other, simply walking to the school in silence. Once they arrived, Rias finally broke the silence by saying, "Emiya-kun, I'll have someone come to get you for a conversation a little later in the day."

They parted ways and headed to their respective classes. When Shirou arrived in his classroom, he was greeted by Issei's shocked expression, who seemed surprised to see him still alive. Issei appeared on the verge of saying something but ultimately stopped and said nothing.

Shirou didn't let anything show on his face, but he was also surprised. He wondered why Rias hadn't altered Issei's memory, as it was the standard procedure when there were witnesses to events they shouldn't have seen.

He should ask her about it later.

The day's classes went smoothly, and Shirou had never felt better. The sword of Damocles that had been hanging over his head had finally disappeared.

He took advantage of the lunch break to make a visit to the restroom to check on a few things with the state of his body, and he was simply astonished. Firstly, his body had returned to its normal state; he had regained his physical abilities. His constitution and soul had changed into that of a demon, in an irreversible manner. However, he had acquired several things. First, he found that he could instinctively summon a pair of black wings from his back. Secondly, his prana had now transformed into demonic power. Another significant change was in his magical circuits. Generally, mages refused to become demons for a specific reason: resurrection as a demon had a high chance of causing the complete disappearance of magical circuits. However, it wasn't without trade-offs. It allowed them to obtain demonic magic, which was far more versatile than that of humans. Still, mages couldn't afford to lose their magical circuits because they were the means to access the Root. Without them, accessing the Akashic Records and true magic became impossible, in addition to losing access to all the magecraft they had trained for And their descendants have a high chance of not possessing magical circuits at all.

However, there are extremely rare cases where the mage doesn't lose their magical circuits but rather mutates into a "demon pattern." This is a form of magical circuit that doesn't have the flaws of conventional magical circuits, such as a fixed maximum output. For example, if a mage was born with a maximum output of 50, they could never exceed that limit and could never use more than 50 units of magical energy at once. The only thing they could improve with these circuits is the speed at which they can absorb mana from the atmosphere to recharge. This continues until they eventually reach overheating. That's why mages have strived over generations to provide the best magical circuits possible to their descendants, often resorting to intermarriage among mages to preserve their lineage.

In the case of the demon pattern, the demon can increase their maximum output, in addition to having faster energy regeneration than other demons. Of course, the demon pattern can also overheat if abused, but overall, it is far superior to any human magical circuit, possessing much higher potential.

After that, he analyzed the tattoo on his hand a bit. He discovered that it seemed to be connected to his magical circuits and resembled magecraft. However, he couldn't deduce its purpose at the moment because it fell outside his area of expertise. He would probably need to reach out to someone he knew for help in discovering its utility. Maybe Rias knew what it was?

Upon returning to class, Shirou noticed the presence of Kiba Yuto engaged in a conversation with Issei. Shirou already knew that Kiba was a reincarnated devil. As he approached Kiba, the latter noticed his presence and spoke to him:

"You're just in time, Emiya. The President wants to see you too."

The two followed the young devil to the occult research club building, leaving several people quite stunned in the classroom."