A dangerous warning

When everyone arrived at the backyard, they found it was already shrouded in black mist. If it weren't for the basic defenses along the edges of the house and the walls of the yard, the fog would have already spread out.

The Black Mist was formless and intangible, showing no inclination to attack, but no one felt safe or harmless either. Everyone stood in front of the back door for the time being, and Rin placed several Gems on the ground to create a barrier.

"This is..."

"I don't know, but it's best not to touch it."

Rin's expression was more serious than ever before. Unlike others, she could clearly "see" the Magecraft, even though she didn't know the true nature of the Black Mist. However, the violent and turbulent flow of magic within it indicated its immense danger.

"Jizi, MSN-100!"

"Learn."

Jizi opened the small bag that had appeared in her hand at some point, took out a Ruby that had been polished into a sphere, and handed it to Rin. The latter carefully controlled the barrier, opened a small opening, and quickly threw the Gems inside.

Upon contact, the Black Mist, like a shark in the sea that has smelled blood, instantly enveloped it, then swirled and coiled around it, trying to find a way to break through and penetrate.

"What is this...?" Shirou didn't know much about Magecraft, asked with some curiosity.

"You can think of it as a probe, analogous to the Deep-Sea Submersible used by scientists," Jizi explained in layman's terms.

"Oh--but will the submersible explode?" Shirou asked another question quite seriously.

"Explode?"

Jizi hurriedly looked over and saw that a lot of Black Mist had seeped into the Gems. It was spinning rapidly inside, and through the surface, many cracks could be seen growing at a visible speed, and the speed was getting faster and faster.

"Cold!"

"I know, but it's too late to retrieve them!"

When the crack expanded to cover the entire surface of the Gems, a muffled thud was heard, and the sphere exploded, scattering fragments in all directions. Some of these fragments flew towards the entrance but were stopped by the Magecraft barrier, leaving black and red marks on the barrier's surface where they were struck.

"..."

"..."

The red-clad female Magecraft and her assistant exchanged bewildered glances; this situation was truly unexpected.

Should we place another probe?

"No, it's no use—absolutely avoid any contact with this thing. Let me think about it some more."

Aside from Projection and enhancement, Shirou knew nothing about other Magecraft. Even though he was anxious, it was useless. He could only watch Rin and Jizi discuss a topic he couldn't understand at all. He wanted to help but was too embarrassed to bother them, so he thought of asking Saber, who should know more than him.

"Saber, you know..."

But when he opened his mouth, Saber also had something to say. Out of politeness Shirou paused for a moment, signaling for her to speak first.

"Master, Jizi, and Rin, don't you guys think this Black Mist looks familiar?"

"Um?"

After hearing Saber's words, Jizi and Rin stopped talking, and then Rin suddenly clenched her right fist and slammed it into her left palm.

"By the way, [assassin]!"

After hearing her reminder, Shirou and Jizi remembered that the [assassin] who appeared during their confrontation with Lancer and their battle with Berserker was also accompanied by this Black Mist. However, the Black Mist was not as aggressive as it was on those two occasions, and Rin had entered it without any problems. In fact, the material that [assassin] used to heal Jizi's serious injuries was also Black Mist.

At this moment, everyone's eyes turned to Jizi, who reached into the small bag containing the materials and pulled out the tattered Mask.

Could it be related to [her]?

"It's only a possibility," Rin said, frowning, "But there could be other reasons."

"Why don't you just ask him directly?" Saber had the lowest opinion of [assassin], hence her harshest tone.

"I'm sorry, I don't want her to come out." Jizi shook her head gently. For reasons still the Unknown, [assassin] needed to possess her body to appear. However, Jizi, who had an instinctive tendency to deny [assassin], did not want to experience that feeling. She was afraid that the increased connection would gradually affect and replace her own existence.

"Jizi..." Lin glanced at her assistant, hesitating to speak.

"Feel sorry."

"... Well, I can't force you, but—oh right, there's another way."

Rin took the Mask in her hand, weighed it in her hand for a while, and then, as if she had made up her mind, she slammed it onto her face.

"Cold!"

Knowing that the Mask a strange Jizi cried out in concern. She herself felt uncomfortable every time she touched the Mask, and only because it was a valuable Magecraft Props did she keep it in her bag; otherwise, she would have thrown it as far away as possible.

"I'm fine."

Because of its rough wooden surface, Rin thought her face would be scratched by splinters and sand after wearing it. However, to her surprise, the Mask fit her skin very well, like a soft face mask, and it even felt as if it had adjusted itself to adapt to her.

There was no opening in the nose area, but breathing was not affected. If it weren't for the two eye openings restricting her vision, Rin wouldn't have felt that there was something covering her face. To test the breathability, she took a long breath and then exhaled.

"Ah!"

The warm air hit the inside of the Mask, and some of it bounced back onto Rin's nerves, making her feel itchy. Just then, she suddenly heard Jizi scream.

"What's wrong?"

"No... it's nothing, I'm just a little itchy."

"Oh."

"Why!?"

Rin casually opened her mouth and uttered an "oh," but Jizi suddenly cried out in surprise.

Are you alright?

"... I kept feeling like someone was breathing on me from behind; it was probably just my imagination because I was too nervous."

"..." Rin had a vague intuition that she had discovered some connection, but that was not the point at the moment. She turned around, walked to the barrier, and stood there. Then she made another barrier behind her, placing herself in the sandwich formed by the two barriers.

"Rin, you didn't mean to—" Seeing Rin's actions, Jizi guessed what she was thinking and hurriedly tried to go over and stop her, but was blocked by a barrier.

"It's okay, trust me." Or rather, I trust [assassin], Rin added in her mind.

"But--"

I'll just give it a try, I'll be right back.

Rin took a deep breath—at which point Jizi shifted her body awkwardly again—then gritted her teeth and removed the outer barrier.

Like a diver entering the deep sea, Rin was instantly surrounded by Black Mist, but the Mask on her face emanated a strange power. The Black Mist did not attack her by spinning as it had when dealing with the probes, but instead slowly surrounded her, as if it considered her one of its own.

"Just as I thought."

Rin tentatively took two steps toward the backyard, but all she could see was a vast expanse of Black Mist, with visibility of no more than a meter. The entire courtyard seemed like another world.

"Bite!"

Just as Rin was about to investigate further, she suddenly heard a crisp sound—the clanging of chains! Remembering that the captured servant used chains with sharp blades at both ends as weapons, Rin decisively retreated to the doorway and raised the outer barrier.

Rin originally intended to use the Gems in her hand to absorb the Black Mist in the isolation space before returning, but as soon as she had this thought, all the Black Mist was absorbed by the Mask and quickly cleared up.

"How about it?"

Back inside, Jizi asked with concern.

"I can't see anything, but the prisoner must have escaped; I heard her voice."

What could be the reason?

"Insufficient information to speculate, but perhaps..." Rin glanced at the Mask she had just removed, "Either it's related to [assassin], or it involves issues from ten years ago."

"The Master who captured the Servant?"

"Unlikely. That woman doesn't seem like the type to pull off something like that. I think she's being used, and her goal might be to cause us some trouble."

"But it also serves as a reminder."

Archer, who had been silently following at the back of the group since the Black Mist appeared, suddenly spoke up, surprising Rin.

You mean--

"Last time, this Black Mist, though not aggressive, forced Berserker back. This time, it allowed the Servant, whom we had completely imprisoned and whose power was sealed, to break free of her cage, and even—"

Archer pointed to the doorway, just like Shirou done before, causing all eyes that were looking at him to turn back.

"Look."

A chained dagger flew out from behind the Black Mist, striking the barrier with the sound of shattering glass. Many cracks appeared on the barrier, but it did not break. However, another dagger quickly flew over as well.

"Careful!"

Rin and Jizi were the first to react. They rushed to the barrier, placed their hands on it, and channeled their magic into it. The reinforced barrier finally withstood the second attack without shattering. But before they could even breathe a sigh of relief, a purple-haired woman's face suddenly emerged from behind the mist and pressed against the barrier.

"!"

This was clearly the prisoner, but her appearance was definitely not normal—at least Rin didn't think anyone could exhale Black Mist from their breath.

"Prepare for battle!"

-----------------------ps----------------------

P. S. 1. I need to replay the HF route; I've really forgotten a lot of things. I'll pause updates until I finish, because I feel like continuing would introduce major bugs.

P. S. 2. Continuing with self-promotion, "The A Certain Scum Top's Itsuka Shiori" has surpassed 100,000 words, unlike the previous 90,000-word rounded-up version! Just click on "The Author Has Also Written" to see it~ Go check it out...