The Overlord of Mysteries

Hello, this is my first time writing a fanfiction. If you notice any errors, please feel free to give me constructive feedback. English is not my first language, so if you notice any mistakes, please mention them in the comment section at the end of the chapter. Let's begin the story!

Word Count: 3600 Words

Note: Just a reminder that I've changed the Guild Auxiliary chapter. I've made some changes to it. I've removed a couple of NPCs and added a few.

Due to my college work, I was unable to upload the chapter sooner so I've made this chapter longer. Increased the word count.

Note:

Also, I was taking some time to improvise the chapter quality, writing quality and whatnot.

It has almost been two weeks since the last upload; as the current chapter I've written has around 3.5k words, I'm uploading it. Lest people don't give this fic a chance, assuming it to be dropped.

Anyway, I've written this fic with patience, which is quite lacking in my previous chapters.

Please rate the chapter and leave a comment on it.

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Fuyuki City, Japan

A red-haired boy walked alongside a black-haired and blonde girl. Reaching their destination, they stopped at the foothills of the mountain. They had come all this way, following the mana they were detecting from the hill.

"Who are we waiting for here, Rin?"

"Just a minute, they will be here, Emiya," Rin answered the one named Shirou.

Hearing her reply, Shirou turned to the blonde female by his side.

"You heard her, Saber. Wait with Rin; I'll go ahead."

"I didn't tell you to go, Emiya. And Saber is my Servant now, not yours. So, don't order her around."

Seeing his recklessness, Rin obstructed his path, trying to stop him.

"Rin, I understand that you want to be careful with the plan, but Sakura is hurting. I can't stand still knowing she's suffering right now. How can you wait here, knowing her life is in danger?"

Rin sighed, seeing his caring side, her anger fading.

"I understand your eagerness to save her, but this is not a situation where recklessness will save the day, Emiya. We should follow the plan."

"But Sakura..." Shirou complained, still unconvinced.

Seeing the situation escalate, Saber intervened.

"Shirou, we should listen to Rin."

"Not you too, Saber," Shirou retorted.

Saber replied calmly, "This is an Avenger we're dealing with. Archer sacrificed himself to save you and Rin. It pains me to know that I was useless in that battle. But from the corruption of the Grail, we won't just be fighting Avenger to save Sakura; we'll be facing other Servants as well."

Rin, sensing the situation was getting worse, stepped forward to comfort Saber.

"You were strong back then, Saber. If you hadn't held Berserker back, Archer wouldn't have had his chance." Rin's words caught the attention of both Shirou and Saber, though she regretted bringing up Archer's sacrifice.

Sensing her shift in mood, Shirou backed off. Saber was saddened by her Master's grief, blaming herself for her lack of strength. Shirou, too, was pained by how the battle had ended. He had stood there, helpless, protected by others.

He clenched his left hand, covered in a red bandage, remembering Archer's sacrifice. His gaze shifted to Saber, 'At least Saber didn't suffer the same fate as Berserker, Assassin, and Lancer. As Rin said, they've been corrupted by the Grail. I can't let the Great Fire of Fuyuki City happen again. I won't let Rin or Saber sacrifice themselves for Sakura.'

Saber, noticing his gaze, looked at him. Shirou's eyes then moved from her to Rin and back to Saber, who remained oblivious to his thoughts. Seeing them safe gave him a small measure of comfort.

Though oblivious to his inner turmoil, Saber wondered why he was staring. Shirou's lips curled into a small smile, feeling reassured by their presence.

His resolve grew stronger, but just as he was about to head off alone, Saber moved into a defensive stance, eyes locked on the forest beside the hill. She was preparing for a fight.

Shirou grew nervous, unsure of how to protect both Rin and Saber. Shirou knew he was weak.

Rin, also sensing the change in the atmosphere, turned towards the forest. The bushes shook, and the man they knew as the Priest walked out from the shadows, followed by Illyasviel.

Shirou held his ground, unsure of what to expect, while Saber remained on alert. Ignoring their unease, Rin addressed the newcomers.

"So, how did it go?"

Illyasviel turned to Shirou and replied, "We took down Assassin."

---

Shirou and the others were stunned by this news. Rin more so than the others, as she had only asked them to survey the field, not expecting Assassin to be defeated. Although pleased by the outcome, the condition of their allies tempered her enthusiasm.

Rin glanced at the sinking sun, sighing as the sunset bathed the scene. She realized it was going to be a long night.

---

Unbeknownst to the group at the foothill, a shadow creature observed them from afar. As an Arch Shadow Demon, its vision and hearing were far superior to others. Despite the distance, it kept its presence hidden, immobile like stone, ensuring it wouldn't be detected.

Watching their gathering, it was reminded of its master, the Supreme One, whose presence had vanished from its radius. As a summon, it could teleport to its master regardless of the distance. Yet, it had failed to sense him anywhere in the world. Although it detected another of its kind in the west, the demon feared it had been abandoned. But the girl it was tasked to protect kept its hope alive.

It had conflicting thoughts about the girl. She was a mere mortal, yet the Supreme One had entered a contract with her. The demon doubted and resented the girl for daring to form such a bond with its master. 'The audacity of a mortal to hope for such a thing.'

Still, it respected her loyalty to the Supreme One. Despite her power and the mysterious Holy Grail that intrigued the demon, what mattered most was her ability to fulfil the Supreme One's wishes.

Its conflicting thoughts aside, the demon was confident in its ability to neutralize her if necessary, even if it couldn't defeat her outright. The girl was loyal for now. But killing her would be easier than neutralizing her. The demon pondered its course of action, considering the other Servants she had supposedly corrupted.

Returning from its musings, it noticed the group was on the move. Needing to return to the girl's side before the pests could arrive, the demon sank into its shadow and headed back to her. After all, it had a duty to protect her—a divine command from the Supreme One.

Right when the Demon was in the process of entering its Shadow, its head snapped towards the city. Particularly towards the Mansion of the Girl.

The demon was overwhelmed with emotion as it sensed the Supreme One's presence again, this time in the city. Overjoyed, it realized it had not been abandoned. Yet its duty to the girl kept it from immediately rushing to its master's side. Reluctantly, it returned to the girl's side, awaiting the moment it could be reunited with its master.

---

Inside the cave, where Sakura and Avenger resided...

Swords clashed at the entrance. A teenage boy with a red bandage swiftly sliced through a giant of a man.

"Nine Lives Blade Works."

Shirou watched as the colossal Berserker fell, his body not splitting despite the blow. He looked at the saddened eyes of his supposed stepsister, Illyasviel, as the end of Berserker's life in the Holy Grail War came to pass.

He watched as the body of the berserker split into specks of light.

"Are you okay, Illyasviel?" Shirou asked, concerned for her well-being and emotions.

Composing herself, Illyasviel replied, "Let's move, brother. We can't keep Saber and Tohsaka waiting."

"Right," Shirou agreed, though he kept his thoughts to himself. 'I'll have time to check on her later. Right now, Sakura is my priority. I can't let anything distract me from saving her.'

They had split into teams to face the Servants. Saber was with Rin, while Shirou teamed up with Illyasviel. The priest was in no condition to fight, so they had left him at the foothills. Now, their only goal was to end the battles quickly.

---

While Shirou and Illyasviel fought Berserker, Rin and Saber were engaged in a duel with Lancer.

As Saber and Lancer clashed, their battle reached new heights. Sparks flew with every swing of Saber's invisible sword and every thrust of Lancer's cursed spear, Gáe Bolg. Lancer's swift, agile movements kept him just out of range of Saber's devastating strikes, but it was clear that the King of Knights was slowly pushing him back.

"You truly are a formidable knight, Saber," Lancer remarked between blows, his voice filled with admiration. "If only you could reveal your name to me. This battle would go down in history as one of the greatest in the Holy Grail War."

Saber, wary of his compliments, focused on his movements. The speed of his spear was deadly, and she knew that a single misstep could cost her everything. She deflected his blows carefully, never letting herself fall into his rhythm. "It is an honour to fight such a warrior as yourself, Child of Light of Ireland," she responded, her voice steady.

Lancer grinned, impressed. "You know my legend, yet I know nothing of yours. What's the fun in that? Why hide your identity from me, Saber? We could turn this into a duel that would be remembered through the ages." He paused, his eyes darting toward Sakura, his master. "But it seems my time is short. My Master demands that I finish this quickly."

Saber stiffened as she saw Lancer glance at Rin and Sakura, and when he suddenly pivoted, making a beeline for Rin, her heart raced. She couldn't let him interfere in Rin's battle with Sakura. Saber moved swiftly to intercept him, her invisible blade clashing with Lancer's spear just in time.

---

While Saber and Lancer were locked in their fierce duel, Rin faced Sakura in a battle of magecraft. The battle, however, was one-sided. Rin's experience and mastery of magic easily overwhelmed Sakura, whose attacks were futile against her elder sister's precise and powerful strikes. Each time Sakura tried to conjure a curse or send out a wave of dark energy, Rin would counter with precision, nullifying her efforts.

Sakura's desperation grew with every failed attack. She glanced toward Lancer, hoping he would come to her aid, but to her horror, even he was struggling againnst Saber. Her heart sank. She had hoped to overwhelm them with Lancer's strength and her own magecraft, but it was all falling apart. Desperation clawed at her, and in a last-ditch effort, she ordered Lancer to cover her, to take Saber out of the equation so that she could focus on Rin.

Lancer's eyes briefly met Sakura's, and though he obeyed her command, Saber was already upon him. With swift and elegant movements, Saber blocked his path, keeping him from interfering in Rin's fight with Sakura. Rin, distracted for a moment by their clash, failed to notice Sakura launching a desperate attack toward her.

But before Sakura's attack could land, a figure stepped between her and Rin. Shirou had placed himself in harm's way, blocking Sakura's strike with sheer determination. "Sakura… this isn't the way," he pleaded, his voice filled with sorrow.

Sakura's eyes widened in shock as she saw Shirou, her attack having no effect on him. Before she could react, Saber and Rin, working together, unleashed their combined might against Lancer. The legendary spearman put up a valiant fight, but in the end, he succumbed to their relentless assault. As Lancer fell, his body fading into ethereal particles, he resisted Sakura's control one last time, freeing himself in death from the chains that bound him.

Rejecting the corruption of the Grail, in his last moments.

Sakura stood frozen, her last line of defense gone. She was truly helpless now, her strength failing her as the weight of defeat settled over her like a crushing wave. Unlike in Heaven's Feel where Sakura faced her sister, Rin alone, this time Shirou, Saber, and Illyasviel were all here to face her together with Rin. But while Saber hesitated out of respect for Shirou and Rin's feelings, both Rin and Illyasviel pressed forward with deadly intent.

Shirou, conflicted and desperate to save Sakura, watched in horror as Rin and Illyasviel charged toward her. Illyasviel's magecraft, deadly and precise, flared as she sent her bird-like constructs toward Sakura, while Rin prepared to strike her sister with the crystal sword, a weapon imbued with the mana of countless multiverse, hoping to end her life.

---

Time seemed to slow for Sakura. She watched as Rin's crystal sword drew nearer, its surface reflecting the cavern's dim light and her own shattered reflection. In that reflection, she saw her past. Moments of happiness and joy flashed across the sword's surface, mixed with memories of pain, suffering, and loss. For the first time in what felt like years, Sakura saw herself as she once was—an innocent girl who had dreamed of being saved by her sister, and of being reunited with her sister.

"Sister…" she whispered, her voice lost in the chaos around her.

The memories were fleeting, but they stirred something deep within her. Despite all the darkness that had consumed her, despite the Grail's corruption and the horrors she had endured, a part of Sakura still longed for the warmth of her family. For a moment, she wished she could have been saved, that she could have lived a life free of the shadows that had engulfed her.

Though she wondered about the anomaly, despite the speed of her thought process, the surroundings and everything had slowed down.

As the crystal sword approached, Sakura's mind drifted to a figure from her past—the Fool, an enigmatic presence that had disappeared the day she met the priest. The Fool had been her hope, her escape, but he had vanished, leaving her alone in the darkness. Even now, she wondered if he might return, if he might save her one last time. But deep down, she knew he was gone.

'He had grown bored of her and the Earth.'

---

Rin's sword was mere inches from Sakura when the impossible happened. A flash of darkness reflected off the crystal blade, and with a powerful force, Rin was pushed back, stumbling as the sword was repelled. At the same moment, Illyasviel's bird-like constructs were obliterated, their forms shattered before they could even reach Sakura.

Saber, Shirou, Rin, and Illyasviel stood in shock as a dark, oppressive energy began to emanate from Sakura's shadow. The very air around them grew heavy as the darkness spread, consuming the cavern in a suffocating void. From the depths of Sakura's shadow, a monstrous form emerged—a demon unlike any they had ever seen before. Its hulking, twisted form towered over them, radiating a power that chilled them to the bone.

Sakura's eyes, once filled with despair, now gleamed with something else—power, fear, and a faint, lingering hope. This demon was not Avenger, the familiar entity tied to the Grail. No, this was something far older, far darker, born from the depths of the Abyss and the aura it gave off, reminded her of the Fool.

Shirou, undeterred by the demon's overwhelming presence, charged forward, his weapon drawn as he prepared to face the creature head-on. But his attacks were useless. The demon swatted him aside as though he were nothing, sending him crashing into the cavern wall. Saber, realizing the gravity of the situation, leaped into action, engaging the demon with all her might.

As the battle raged on, the demon's power continued to grow. Shirou, Rin, and Illyasviel fought desperately, but it was clear that they were outmatched. The cavern echoed with the sound of steel clashing and magic flaring, but the demon remained unyielding, its form a terrifying reminder of the darkness.

And as the battle continued, one thing became painfully clear: this fight was far from over.

---

Shirou watched as Saber valiantly engaged the demon, her sword shimmering in the dim cavern. Each of her strikes was precise, powerful, yet every blow met the dark, unyielding form of the demon. The creature flinched, its strength or Saber's swordsmanship skills seemingly lacking to that of it. The cavern echoed with the sound of clashing steel, and the oppressive darkness of the demon's presence hung in the air.

"Stay back, Shirou!" Saber shouted, her voice strained from the effort of maintaining the relentless attack.

Rin, still recovering from the sudden pushback by the demon, gripped the crystal sword tighter. She was breathing heavily, shocked by how effortlessly her attack had been deflected. "What is that thing?!" she muttered, more to herself than anyone else.

Illyasviel, meanwhile, was preparing another round of magecraft. Her bird-like constructs fluttered around her, ready to be deployed. "That demon… it's protecting Sakura," she realized aloud, her voice tinged with frustration. "If we don't figure out how to get past it, we won't reach her in time!"

Sakura stood still in the center of the chaos, her wide eyes reflecting the battle. The demon had arisen from her shadow, a guardian she hadn't summoned but somehow knew was there to protect her. Yet, it wasn't the Avenger she had come to know. It was something else, something darker, and more ancient. Her heart ached with confusion and fear. She hadn't wanted this. She hadn't wanted any of this.

"Saber!" Shirou called, his voice hoarse from desperation. "We need to break through! We can't let Sakura—"

His words were cut off as the demon swung its arm in a wide arc, sending a shockwave through the cavern. Saber leaped back, barely avoiding the impact, but the force sent both Rin and Illyasviel stumbling backward. Shirou fell to the ground, shielding his eyes from the debris kicked up by the demon's strike.

"It's too strong," Saber muttered, her expression grim as she landed beside Shirou.

"Then what do we do?" Shirou asked, trying to keep the panic out of his voice. "We can't just stand here!"

Rin, having regained her footing, glanced at the crystal sword in her hand. The Jeweled Sword Zelretch. The sword with infinite mana.

"We can't destroy the Demon, fast enough before the Grail does its work. We should deal with Sakura as soon as possible."

Illyasviel, her face pale but determined, nodded.

"But how do we get to her?" Shirou asked, glancing toward the towering form of the demon. "That thing won't let us near her."

Saber looked at the demon, her grip tightening on her sword. "I'll create an opening," she said, her voice resolute. "You three focus on reaching Sakura. I'll hold off the demon as long as I can."

"No!" Shirou protested, his heart pounding. "Saber, you can't—"

"This is the only way, Shirou," Saber interrupted, her eyes softening as she looked at him. "Trust me. I won't let this creature stand in our way. Though it has its unusual attacks, it still falls short of sword skills."

Before Shirou could argue further, Saber rushed forward, her blade raised high as she engaged the demon once again. Her strikes were relentless, each one forcing the creature back, if only for a moment. The demon roared, its blackened form shifting and twisting as it tried to keep up with her assault.

"Now!" Rin shouted, grabbing Shirou's arm and pulling him toward Sakura. "We don't have much time!"

Shirou, Rin, and Illyasviel ran toward Sakura, who stood frozen in the center of the cavern, her face a mixture of fear and sadness. The closer they got, the more they could feel the weight of her despair. It was suffocating, like the very air around her was tainted by her emotions.

"Sakura!" Shirou called out, his voice cracking. "We're here to help you! Please, let us help!"

But Sakura didn't respond. Her eyes were distant, lost in the memories that consumed her. The corruption of the Holy Grail swirled around her, feeding on her anguish, her guilt.

Rin stepped forward, holding the Jeweled sword out in front of her. "Sakura, listen to me!" she shouted, her voice fierce. "You don't have to carry this burden alone! We're your family! I'm your sister! And I won't let you fall into this darkness!"

Sakura's eyes flickered, the faintest glimmer of recognition shining through the haze of her despair. "Sister…?"

Taking her chance, Rin lunged forward, the crystal sword aimed directly at the heart of Sakura. The sword's surface glowed with an ethereal light, reflecting not only Sakura's visage but Rin's determination, her love for her sister. She had the resolve to kill her sister to save the city.

---

The Arch Shadow Demon sensing the attack on mortal girl, sunk into its shadow. Saber an inch away from reaching the Demon.

The Arch Shadow Demon, stood in-between Sakura and Rin. Leaving Saber empty, as it swatted them off once again.

Far away in the shadows, the remnants of Avenger stirred. The fight for the future of Fuyuki City and the souls intertwined with the Grail had only just begun.

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**The End**

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