Having nothing to do is actually an incredibly unsettling feeling.
For a hero who has traversed battlefields, never having idle time to spare, boredom is akin to a natural enemy.
The "Red" faction has been holed up inside "Red" Assassin's aerial fortress ever since, never once sallying forth.
There are all sorts of heroes, but those summoned in Holy Grail Wars are generally warriors. Naturally, they possess a desire to showcase their martial prowess, to fight.
However, the current "Red" faction is in the midst of turning its back on the "Black" faction and fleeing; they are not in a situation to cross blades with the enemy. Their spirits inevitably slacken, and they are left bewildered with nothing to do.
To "Red" Rider and "Red" Archer, who look bored and listless, "Red" Assassin speaks with a bewitching smile.
"It seems even a great hero cannot triumph over boredom."
"If there was an enemy named 'Boredom' right in front of me, I'd blast it away."
"How restless."
Assassin, still wrapped in an eerie charm, has a Dragon Tooth Warrior pour wine into a golden cup.
"What, want some?"
"Nah. Actually, the only one who'd accept that cup knowing your True Name is that guy."
Rider is referring to Assassin's Master, who isn't present.
Assassin makes a complicated expression and moistens her lips with the wine. Then, she glares at Rider, who still seems to want to say something.
"What?"
"It's just... that Master of yours who seems utterly lacking in personal desires, and you, Empress, who seem like the embodiment of them, getting along so well."
"Do you have some complaint about him even now?"
"Don't get angry, Empress. My stance is that I'm willing to lend a hand to his ideals, separate from whether I acknowledge him as my Master. I'm not in his service, so it's not disloyalty, right? Even your Master recognizes that point regarding this matter."
"Sophistry."
"Heh, I'm only stating facts, though."
Instantly, lightning assails Rider.
After a dazzling light flashes through, Rider is gone.
Assassin lowers her raised hand and glares at Rider, who has jumped onto a Renaissance-style sculpture in the corner of the room.
"That was dangerous."
"Just right to reduce your impudent mouth."
Faced with Assassin's hostility, Rider is composed.
Assassin's lightning strike could penetrate Rider's immortality, yet Rider still taunts her. He already accounted for counterattacks.
"What's all the commotion?"
Arriving there is Amakusa Shirou himself.
He looks back and forth between Assassin holding the cup and Rider squatting on the statue with a puzzled expression.
"It's nothing."
"Is that so?"
Shirou shows no particular interest and doesn't press further.
"Master, did something happen?"
"No, the Grail has stabilized, so I thought it was about time to scout the other side. Therefore, I'd like you, Archer, to go out as a scout."
Shirou turns his gaze to Archer.
"Hmm, well, if it can somehow alleviate this boredom, I don't mind anything."
The 'Archer' class has the 'Independent Action' skill. This skill, allowing action even without a Master, is suitable for scouting, similar to the 'Assassin' class's 'Presence Concealment'.
"Hey, what about me?"
"I don't think there's anyone less suited for scouting than you."
Casually excluding Rider, Shirou continues.
"If any problems arise, please contact me via telepathy. I'll support you with a Command Spell."
"Is it alright to use a Command Spell for such trivial matters?"
"Unlike the Ruler over there, I received Command Spells from Masters, so I can use them on all Servants under my contract. I have some left over from Berserker, so it's not a problem."
"What a luxurious way to use them."
Without changing his expression, "Red" Archer runs his hand through his hair. It's not a gesture meant to beguile men like Assassin's; it's a wild, almost dismissive motion, as if brushing something aside.
"Well then, I'm off. I'll rely on a Command Spell for the return."
"Yes, I understand. I'm counting on you, Archer."
"Red" Archer leaves for his scouting mission without looking back.
"Red" Archer, though initially furious when his Master rights were usurped, has come to find aspects of Amakusa Shirou's wish resonant and has reached the point of acknowledging him as his Master.
While she is a Heroic Spirit, she is not a hero in the sense of a warrior.
She doesn't possess the warrior's pride like "Red" Rider, and regarding her former Master, her feelings lean more towards dismay at his carelessness in being poisoned during the Grail War.
Ultimately, she is a realist, and in a world of life and death, showing openings is a mistake.
Therefore, if Amakusa Shirou's wish is convenient for her, there was a sufficient possibility she would side with him. And the salvation of all humanity overlaps with Archer's own wish.
If a world where all children are cherished lies beyond Shirou's wish, then realistically speaking, it's obvious that siding with him is better.
If he intends to make even people from the past immortal, she, as a Heroic Spirit, might vanish, but such a thing was a mere triviality.
Those participating in the search for "Black" Assassin are Ruler, Celenike, "Black" Rider, Caules, and "Black" Berserker. Though the combat abilities of the "Black" Servants are low, considering Assassin's combat power, having two Servants should be sufficient, and the presence of Ruler, a high-ranking Servant, means their force is adequate.
Since it's still a time with people around, the Servants are kept spiritualized. They walk through the town, with Ruler—who cannot become spiritual while possessing Laeticia's body—at the front.
Caules asks Ruler,
"Ruler, can't you pinpoint Assassin's location?"
"Let's see... My perception extends to about ten kilometers in all directions, but an Assassin with 'Presence Concealment' can only be roughly identified. They are definitely in this town, but I can't specify the location."
"Then, I guess we have to go through them one by one after all."
In Trifas, magi from Yggdmillennia had been hiding and providing rear support. Of those, a full ten have lost contact.
"First is Karl Lexam. A mage living just a little further ahead."
Karl lives in the new urban district of Trifas. It's an old-fashioned stone house, nearly cubic in shape. A closed-off environment is preferred by magi. Magical energy dissipates less easily, and concealment is simpler. Thus, for an environment conveniently hidden for secret experiments, a stone building becomes a natural choice. Though called the new district, it was established after the Ottoman Turks were repelled, so medieval Western architecture lines the streets. That the heartland of magecraft is in the West might have such reasons.
The interior of the house is simple, apparent even from outside.
A living room, washroom, and kitchen. The interior lacks personality and feels unlived-in. Even a model room would feel more inhabited than this.
Materialized, Rider rummages through the interior as if he owns the place.
"Rider. It's someone's house, so please try not to make a mess."
Ruler chastises Rider. However, Rider either doesn't take it seriously or is already convinced there's no need to consider the house's resident, as he continues pacing back and forth.
"Hmm, smells like blood."
Then, Rider says while looking up at the ceiling.
"Is that so?"
Ruler looks towards Caules and the others.
Caules shakes his head; Celenike narrows her eyes and looks around the room. Apart from Rider, no one else can sense it.
"Perhaps it's just your imagination?"
"No, that's not it."
Celenike denies Ruler's words.
Celenike uses magecraft, searching the room with magical energy. It's a spell that reacts to blood, causing the target to glow faintly.
The effect is immediate.
They can see blood splattered all over the room. Though invisible to the naked eye, the fact that it's thinly smeared suggests it was wiped.
"It's been cleaned?"
"Ordinary magi wouldn't leave blood in their own domain."
"So, the owner of this house wiped it?"
"Who knows? A proper mage wouldn't make such a blunder as to spill blood conspicuously here. Though there might be some from dressing small animals."
Celenike directs her gaze to Rider.
"Rider, anything else catch your attention?"
"Hmm, seems like there's a basement."
Rider had found the entrance to a basement hidden under a bookshelf in the corner of the room.
It seems he noticed its existence from a slight creak while walking around the room.
"How did you know?"
"Sound and smell are necessary on the battlefield."
Casually answering, Rider steps into the basement.
Entering a mage's workshop is suicidal, but it's meaningless against Rider's 'Magic Resistance.'
"Found a body!"
After a few fluctuations of magical energy, Rider calls out from inside the basement.
Traps seem to have been activated several times, but Rider appears to have broken through them all and achieved his goal.
"Bringing Rider was the right decision."
Watching this, Celenike and the others follow behind.
Inside the basement, a faint magic circle remains, suggesting some ritual was performed. Seeing small animals like mice and pigeons, mummies, and small vials hanging from the ceiling, this mage seems to have been a practitioner of black magecraft.
"Whoa... Pretty decomposed."
"Rider. Please don't say such things."
Ruler chastises Rider for his words as he flips over the face-down corpse.
The body is several days post-mortem, emitting a strong putrid odor.
"The heart has been gouged out."
"Cause of death is severed carotid artery. The heart seems to have been gouged out afterward."
"Just as reported in the papers. We can safely assume it's Assassin's work."
Celenike kneels beside the body, examining it.
As an exceptionally skilled black magician who has lived among corpses, Celenike is accustomed to such situations.
"We can say there's virtually no magical intention. The heart... well, probably used for soul consumption."
"So, they were killed just to consume the heart?"
"Judging from this body, that seems to be the case."
Servants are spiritual bodies, so they can accumulate power by consuming souls. In Assassin's case, they probably gain power by taking others' hearts.
"I wouldn't want to eat a human heart."
"That's normal. It's just that the Assassin isn't right in the head."
Caules says to Rider, who grimaces.
"Anyway, based on this alone, we can't say much. From the situation, it was nearly instant death. The victim probably died without even knowing what happened. Let's move on."
Somewhat saved by Celenike's matter-of-fact words despite the bizarre circumstances, the group nods and leaves the basement.
A body was also found at the next mage's house they visited.
However, the situation here was far too different.
"This is..."
"It's beyond recognition. Though the heart seems gouged out. Torture again, perhaps?"
The discovered body had been thoroughly violated.
The only similarities to before are the fact of being killed and the heart being gouged out. It's barely identifiable as a corpse; even the gender is unclear.
Similar bodies were found consecutively after that.
They visited seven of the ten mage households that were search targets, and the majority showed signs of severe assault.
The eighth body was also killed with the heart gouged out, but the physical damage was a spectacle one would want to look away from.
"This is like... human meat, 30 grams, how many Euros?"
"Rider, don't say weird things."
Caules says to Rider while averting his eyes.
Ruler, worried about Caules, speaks to him.
"Are you alright?"
"Yeah, somehow..."
Perhaps his senses are becoming numb; he calmed down after vomiting once at the third scene. Thinking that this will surely haunt his dreams later makes him gloomy already.
"Celenike, do you understand anything?"
"Well. First, the lack of any trace of magecraft is concerning."
"Because Assassin isn't a mage?"
"But there's a Master, right? There were two types of footprints in this house besides ours. One was from heels. If not Assassin's, then the Master's. This body is male, right?"
"Y-you noticed that well."
The bloodstains were wiped, but it seems they didn't think about footprints.
The footprints Celenike pointed out were one right inside the entrance and two in the basement workshop. Since the types increased to two in the basement, the newly added one should be Assassin's footprints. This mage was attacked in the workshop.
"Assassin's Master is female."
"Unless it's a cross-dressing fetish. It's also questionable if they're a mage. If they're making Assassin consume souls this frequently, it might indicate they can't supply Assassin with magical energy."
"Controlling Assassin without being a mage?"
"It's just speculation, but a mage would probably avoid actions that get reported in the news."
"True."
'Mystery must be kept hidden' is an iron rule a mage should uphold even in death. The fact that not only is this not strictly followed, but they didn't even try to hide it initially, suggests they don't understand the basics of being a mage.
"Recently, they seem to be targeting magi specifically. Since a mage's heart is like a source of magical energy, it's probably more efficient than targeting ordinary people."
"But then, why such cruel methods of killing?"
If they only wanted to consume the heart, they could kill normally. Like the first one they found, Karl.
"Normally, it would be because they tortured them."
"So, that's it."
"Judging from the wounds, it looks like they deliberately avoided vital points to inflict effective pain. They definitely tortured without killing."
The varying degrees of bodily damage probably depend on how long it took to extract the necessary information.
"Hey. If they tortured, they must have wanted information, right? What did Assassin want to know?"
No one could answer Caules's question.
Only those present at the scene would know.
"No helping it. I'll replay the residual thoughts."
"Are you sure?"
"I'm a black magician. The torture of a mere murderer is nothing to me."
By replaying residual thoughts, they can understand what kind of horrific event occurred in this room. Though not perfect, the victim's final agony will be replayed within Celenike.
It's quite a risky magecraft for the caster as well.
If they synchronize too much, they might feel the victim's pain directly.
However, for someone like Celenike, subduing that pain is probably easy, and she won't make mistakes. She can replay the victim's final moments in her mind dispassionately.
Celenike sits on a chair and takes a small vial from her pouch. Inside is a clear liquid.
"I'm going to synchronize now. It won't take five minutes, so do as you please around here."
"'Do as you please'..."
Ruler looks at Celenike in disbelief.
She has already licked a drop of the elixir, closed her eyes, and begun synchronization. Celenike is about to use extremely dangerous magecraft, yet she remains composed.
However, the others left behind feel complicated.
After all, this place is an all-too-gruesome murder scene. A putrid smell lingers, and terror is etched on the corpse's face.
Wondering what to do, Ruler and the others exchange troubled glances.
Meanwhile, Celenike's body trembles.
She has synchronized with the victim's final moments. The pain the victim felt at the end is now flowing into Celenike's body.
"Pain sensation, block."
Celenike's trembling subsides.
For an exceptional black magician like Celenike, pain is not a significant problem. Manipulating pain sensation is a basic of black magecraft. She knows not only how to inflict pain on others but also how to handle it when it rebounds on herself.
In less than five minutes, Celenike's magecraft is complete.
Celenike looks up at the ceiling after it's all over and lets out a breath.
"Are you alright?"
Ruler timidly asks Celenike. Celenike wipes the sweat on her forehead with a handkerchief and says she's fine.
"Really, that Assassin hits human weaknesses precisely."
"Did you find out?"
"Sort of. That Assassin was asking about methods to infiltrate the fortress."
"What...?"
Ruler's eyes widen in surprise.
Caules and Rider are also frozen.
"Th-that's bad! So, what happened!?"
"They talked almost instantly."
"Gh!"
Caules breaks out in a cold sweat.
"Black" Assassin seems to be a highly logical personality.
Rather than blindly challenging the fortress, they investigated the details of the defensive systems, extracted information on their vulnerabilities, and then moved to attack. No matter how sturdy the walls surrounding it, they cannot repel an Assassin with 'Presence Concealment.' Only multiple layers of barriers can block an Assassin's infiltration. If those barriers can be bypassed, then the magi residing in the fortress are essentially in a situation with Assassin's blade at their throats.
"Caules, contact Fiore!"
"I know!"
Spurred by Ruler, Caules rushes out of the basement.
'Sis, are you alright!?'
'Caules, what's wrong all of a sudden?'
The telepathy connects, and hearing Fiore's voice, Caules feels relieved.
'Just now, Celenike replayed residual thoughts and extracted information about Assassin.'
'Oh, is that so? Did you find out anything?'
'Review the fortress's security immediately. Assassin likely knows how to infiltrate the fortress. Keep Archer by your side and don't show any openings.'
'What did you say? Is that true?'
'Yeah.'
Fiore on the other end of the telepathy also seems quite flustered.
Protective barriers via bounded fields are similar to computer antivirus software. If judged harmless, even a malicious entity can slip through.
'Understood. I'll tell Uncle Gord right away, so rest assured. And then——'
Just as Fiore is about to continue something, snap, the telepathy is severed.
For a moment, Caules's mind goes blank.
Telepathy, exchanging thoughts through a magical connection, cannot be severed except by magical means.
In other words, the severing of telepathy with Fiore means something has occurred that blocks the path between Caules and Fiore.
"Did something happen, Caules?"
Ruler, reading the change in Caules's complexion, asks.
"The telepathy with Sis was cut. Something's wrong."
"Let's hurry back. Even gaining just a little information about Assassin means today was productive."
"Black" Saber and "Black" Archer are in the fortress. Even if "Black" Assassin attacks, they probably wouldn't just let the Masters be assassinated, but the possibility exists.
Caules and the others hastily open the door and rush outside.
The sun has already set, and night darkness has spread.
Due to the serial killer's appearance, there are no pedestrians. The silent town feels as if it has stopped.
The first to notice the anomaly is Caules.
"Gh——"
Suddenly, his skin stings.
Thinking it might be his imagination, next his mucous membranes—eyes, throat—burn with pain.
"Aah, it hurts!?"
He crouches down from the intense pain.
It feels like his whole body is burning; he can't keep his eyes open. His throat hurts, making it hard to breathe.
Behind him, Celenike collapses similarly.
"Caules! Celenike!"
Ruler rushes to the two and wraps a thin, reddish cloth around their faces. Then, breathing becomes easier. Looking through the cloth, they can see outside.
The cloth wrapped by Ruler possesses magical energy, its power seemingly blocking external interference. The skin still stings, but their faces are somehow manageable.
"It's a Shroud. This should mitigate the effects of this fog somewhat."
Fog?
Only when Ruler says this does Caules notice the fog.
Though hard to tell at night, it appears somewhat yellowish. A sour smell assaults his nose, making him grimace involuntarily.
"It must be 'Black' Assassin's ability. It seems they've targeted us, not the fortress. Please stay on guard."
"Black" Berserker materializes as if to protect Caules.
Rider also readies his spear, scanning the surroundings, and Ruler arms herself with armor and flag.
Visibility is poor in the fog. However, there are three Servants here. No matter who "Black" Assassin is, common sense dictates that if they pick a fight, they will be defeated.
Even if they sneak up with 'Presence Concealment,' when they shift to an attack posture, that rank drops significantly, making a response possible.
They will defeat Assassin when they sneak up.
But, for some reason...
Ruler feels that won't be enough. She doesn't know why, but if things continue like this, a fatal problem will occur-.
There are five prey.
Three Servants and two Masters.
Initially, they intended to infiltrate the fortress, but assassinating Masters in a fortress guarded by Saber and Archer is dangerous, so it was postponed.
Priority is the woman first.
Of the five who came out of the mage's house killed earlier, three were women. One is a man, and the other is hard to tell. There's also a Servant that seems like a machine. The uncertainty of what counterattack might come is unsettling.
It's probably best to aim for the Masters to be sure.
And so, Assassin sneaks up on the chosen prey.
In the sulfuric acid fog, all conditions are met. Now, Assassin is permitted to take the initiative against any enemy.