Black Mud Heroic Spirit Holy Grail
Shirou exchanged a glance with Yukinoshita and Yuigahama, then dashed straight out.
The moment an otherworldly monster was sensed to be invading, the world's consciousness activated its defense mechanism, erecting a barrier of alternate space to protect the real world behind a membrane.
A humanoid figure made of massive stones, towering over ten meters tall like a high tower — this was a greatly enlarged version of a ruin guardian.
Due to mutation, its entire mineral body had transformed into diamond. It raised its right foot high and stomped fiercely on the wall of the alternate space.
This caused a muffled thunder-like sound to resonate through the real world.
Behind the ruin guardian, there was a huge cavity leading from the otherworld to this place, from which countless wing-blade insects flew out.
"Reins of the Heroic Steed (Bellerophon)!"
A comet—a black comet trailing a long tail—descended from the sky.
Riding the black pegasus within the black light was a man who repeatedly used his Noble Phantasm, relentlessly assaulting the alternate space defense barrier.
Under the black comet's repeated impacts, the surface of the protective membrane began to crack.
The real world, within the inner wall of the alternate space, trembled once again.
"Ah! An earthquake?" a child inside screamed.
"This is bad! There are still so many children here!" Yukinoshita exclaimed.
"Leave it to me!"
Shirou, using possession summoning, channeled Merlin and cast a powerful illusion at maximum magical output.
He envisioned a calm and ordinary daily life, transforming the space into that image.
The house where the children were was enveloped in the illusion, and the children inside were subconsciously influenced to feel calm, relaxed, and dissuaded from going outside.
They felt everything was just as usual and could no longer sense the tremors outside.
"Eh? It's not shaking anymore? Was it just my imagination? That was weird. You guys felt the quake earlier too, right?" the previously screaming girl asked in confusion.
"Hmm… it felt like there was, but then maybe not?" The girls exchanged puzzled glances, each uncertain.
"Looks like it was an illusion. Let's keep going."
"Yeah."
So, the elementary school girls continued their work as before.
Under the illusion's effect, people nearby also relaxed and carried on with their activities inside the building.
Just then—
BOOM!!! The black comet finally broke through the membrane.
A black-skinned man riding a black pegasus floated into the real world, glaring angrily ahead, and let out a beastly roar.
"Shirou! Be careful, this Heroic Spirit is way too abnormal!" Da-chan flew out from the phone and shouted.
Shirou opened his Mystic Eyes and observed the black Heroic Spirit.
The man was a hero from Greece, son of Zeus, beloved by the gods.
Unlike Heracles or Achilles who were famed for their brute strength, this one achieved greatness through using numerous divine Noble Phantasms granted by the gods.
He was known for slaying the rampaging immortal monster Gorgon and saving countless lives.
But this Heroic Spirit now, having been tainted by black mud, had eyes filled only with hatred. In his hand was the Noble Phantasm "Reins of the Heroic Steed (Corrupted)".
His body had been corrupted into a being of Chaotic Evil.
After being eroded by the black mud, his abilities had been altered to a degree.
Enhanced by the Holy Grail's amplification, what was once a Noble Phantasm used to empower his steed Pegasus had now become a tool to summon and command large numbers of monsters.
"Hyah!" Yuigahama rushed out shouting, immediately using possession summoning to transform into Suzuka Gozen, and leapt forward with a slash aimed at the black Heroic Spirit from behind.
"Hmph!" The black pegasus was incredibly fast and easily evaded the girl's strike, darting back into the broken membrane fissure and vanishing.
"He escaped?" Yuigahama landed with a frown, sword in hand.
"This is bad! They're coming out! The monsters are invading the real world! Over a hundred magical reactions! One of them is massive!" Red dots flooded the phone screen as Da-chan cried out in panic.
"What!?" Shirou exclaimed.
With a boom, a massive diamond foot kicked apart the membrane, which had already cracked from the comet strike. A diamond giant, several tens of meters tall, crawled out and officially appeared in the real world.
This was the first time a monster had emerged where people were present.
At this moment, the second line of the world's defense mechanism quietly activated.
A world that originally repelled all forms of mystery now changed due to the monster's intrusion into reality.
It became much easier for connections to form between humans and Heroic Spirits.
Under the command of the black Heroic Spirit Perseus, swarms of wing-blade insects surged from the cracks of alternate space and flew toward the building.
"Not a chance!" Yukinoshita, who had been guarding the entrance, pulled out her phone, preparing to summon Ushiwakamaru to fight. No matter what, she would never let the children inside be harmed!
"The children must not be harmed!" A voice echoed from the void into Yukinoshita's heart.
At that moment, another entity responded. A golden frame flickered with light.
"I understand!" Without hesitation, Yukinoshita tapped it.
This time, it wasn't a girl summoning a Heroic Spirit to possess her, but rather a Heroic Spirit in Chaldea who sensed that children here were in danger.
Their wish resonated with the girl's wish, and they sincerely entrusted all their power to her.
Possession Summoning.
Compatibility: 100%.
Archer-Class Heroic Spirit: Atalanta.
A cool and handsome girl with feline ears appeared within a pillar of light, wearing a green dress. Her tail extended from beneath the skirt. She stood proud and dignified, eyes blazing as she looked ahead.
Yukinoshita backflipped high into the air, landing on the balcony of a building.
She looked down at the swarm of incoming flying insects, completely unfazed.
At 100% compatibility, with Atalanta entrusting her with all her power, this was no longer a simple summoning.
In this fusion of human and Heroic Spirit souls, a kind of ascension occurred.
At this moment, the girl felt she had stepped into the realm of the divine, possessing the peak power of the Greek hero Atalanta.
"Shirou!" Yukinoshita shouted, drawing her bow and pulling it into a full circle.
"I got it!" Shirou instantly understood and raised his wand to cast as much reinforcement as possible, using the Reinforcement Magic, one of the only two types he excelled at.
After gaining Merlin's experience, he had reached Grade B!
"As long as I'm here, no monster will pass through this place!" Yukinoshita raised the Heavenly Bow gifted by the goddess Artemis. From the moment she entered the Heroic Spirit possession, the anti-army Noble Phantasm had already reached 300% charge.
A stream of light shot toward the sky — Phoebus Catastrophe.
The girl prayed to the sun god Apollo and moon goddess Artemis.
A rain of a hundred light arrows fell from the sky, piercing through all the wing-blade insects. The remaining light arrows rained down on the head of the diamond ruin guardian. Its massive body was continuously struck by the falling arrows.
"It's not over yet!" Yukinoshita cried out. She pulled the Heavenly Bow to full draw once more, the arrow's power instantly rising to Grade A, aiming repeatedly at the giant's head.
Each shot exploded like a missile — Boom! Boom! Boom!
The diamond giant's head shattered under the joint assault from above and the front, consumed by the light arrows, and turned into black dust, vanishing.
"So cool, Yukino!" Yuigahama praised in awe.
"Well done, Yukinoshita." Seeing the monster that threatened the world finally defeated, Shirou looked at the black-haired girl and praised her.
"Die!!!"
With no warning, the black Heroic Spirit who had hidden inside the black hole earlier suddenly emerged from the alternate space.
The black-cloaked man appeared behind Shirou, holding a scythe-like sword, swinging it straight at Shirou's neck.
"Hyah! Shitidehanin — Vajra Pestle!!!"
A Vajra pestle crackling with lightning transformed into a thunderbolt, striking the black Perseus and blasting him away. (Vajra Pestle is a ritual object in Vajrayana Buddhism, a symbol of wisdom and power, representing the indestructibility and strength of lightning.)