Kwakwakwakwakwaka!!!!!!!!!!
"That's... Tohsaka, right?"
Rin used the Kaleidostick, and the Kaleidostick Ruby had received information from a worldline among parallel worlds where she had met Fergus. And she forcibly reproduced that power, the power used by the Ruby from that place, just once.
Although she sacrificed the Tohsaka Magic Crest as a side effect, for Rin, that much didn't matter. Because it was the last means to save her sister.
Rin, who received the story of the parallel line from Ruby, used the power to let Scáthach possess her, the only means to deal with Fergus. And, since it was a separate recreation from Fergus's class card and because Scáthach herself responded strongly, her body was perfectly recreated in the form of a Servant.
Rin, having handed everything over to Scáthach, fell asleep, and Scáthach expressed her gratitude to such Rin and continued the battle with Fergus.
"Go, boy!"
"Ah, yeah!"
Scáthach shouts to Shirou, and Shirou runs towards Sakura. Shadows block Shirou's path.
Kagagagang!!!
Shirou deals with the shadows using Archer's left arm, which is like a sword, and advances forward.
"Move aside, Scáthach!!!!"
"Sorry, but I can't do that!"
Fergus, using the Grail's magical energy, fires thousands of magic bullets on the level of Anti-Army Noble Phantasms. Scáthach swings her demonic spear combined with primordial runes, cutting down all the magic bullets. Then she throws dozens of crimson demonic spears.
Soon, Fergus draws dozens of primordial runes in the air. Originally, using such magecraft would be reckless, close to self-destruction, but he uses it without burden thanks to the Grail's magical energy. Soon, the primordial runes flash, and the staff he was holding multiplies into hundreds of daggers.
"{Curtana Bolg}(The Slashing and Piercing Daggers of Instant Death)!!!"
Shushushushushuk!!!!
A baptism of hundreds of Noble Phantasms pours down, all of them were pursuit-type Noble Phantasms like Gáe Bolg.
Soon, Scáthach's demonic spear, her crimson eyes flashing, burns with a red light.
Kwakwakwakwakwakwakwa!!!!!!!!!
".... You've become much stronger."
1500 years have passed since Fergus died. Had he not existed, Scáthach would not have desired a higher realm nor grown while wishing for someone to kill her. However, Fergus's existence changed her. A divine realm warrior who has already entered the realm of immortality anyway. She knew that Fergus held guilt until his last moment. She worried that he might take the wrong path, and in that case, Scáthach...
She had trained continuously for 1500 years to correct such a Fergus. Now her spear has reached a realm incomparable to when Fergus was alive 1500 years ago... a realm where she could kill god-kings like the deity Zeus with just her spear. Even if it was a god, she could kill it.
By the standards of 1500 years ago, Scáthach already had the qualifications of a Grand Lancer, but now...
Kwaaaaaaaang!!!!
"This is insane..."
She had entered such an absurd realm that even Fergus felt something called fear.
Space Piercing.
If Fergus mastered sword slashes that cut space, over the past time, Scáthach entered the realm of piercing space. No matter what attack Fergus launched, she pierced through space and nullified the attack.
Tadat!!!
"I can't see!?"
Scáthach accelerates at a speed that even Fergus's Clairvoyance, used with the Wisdom of the Abyss, cannot keep up with. Over the past 1500 years, she used the Wisdom of the Abyss without reserve and honed techniques of humans who would reach the pinnacle of nothingness in the future.
Among them was the footwork of Okita Souji, who is connected to Fergus in a certain worldline. Scáthach, with speed fundamentally no less than Medusa's, or even greater, exceeds the speed of sound, dodging all of Fergus's attacks and closing in.
"Kh... try dodging this too!!!!!"
Now having deployed a barrier for the Grail and Sakura, Fergus fires a magical energy cannon powerful enough to blow away the entire cave. Scáthach then takes a breath and draws a crimson sword. Among the many weapons she used often in life, a demonic sword made from Curtana's bones, like Gáe Bolg.
Seokeuk!!!!
"... Tsubame Gaeshi?"
An unavoidable demonic sword. A demonic sword where three consecutive slashes strike simultaneously three times is swung, Scáthach using the same space-cutting technique as Fergus. Scáthach precisely cuts only the positions flying towards Fergus, Shirou, and Medusa who recovered belatedly and came running, nullifying them.
"Kh.... Uoooooo!!!!"
Fergus uses the Grail's power to summon Caladbolg, which he normally cannot wield, and grips Caladbolg. Fergus was now desperate. While using Caladbolg, he planned to use teleportation on the Grail to send it elsewhere and die together with Scáthach. He no longer needed Sakura. Thinking to directly create a new vessel and complete the Greater Grail, he planned to wipe out not just Fuyuki but the entire Japanese archipelago. He believed only that much... would allow him to defeat her.
While blocking her with continuous True Name releases of Curtana Bolg, he performs Caladbolg's True Name release. Even if Gáe Bolg couldn't stop him, even if he tried to die together with causality reversal... it couldn't be stopped. With just the Grail's magical energy, even instant death by Gáe Bolg could be regenerated from. Fergus could do it. With Angra Mainyu's power, it was possible.
"{Gáe Bolg Alternative}(The Flying Spear of Death that Pierces and Penetrates)!!!!"
Soon, Scáthach's spear thrown with all her might flies, and Fergus also releases his True Name.
"{Caladbolg Caladbolg}(Extreme - Rainbow Sword)!!!"
A divine construct that shatters the world is swung...
Pajik!!!
Simultaneously, Shirou reaches Sakura and stabs her with Rule Breaker, severing the connection with the Grail. The vessel disappears and the Grail becomes incomplete. Still, Fergus thinks it's no problem...
"Answerer"
"──That is."
Soon, Scáthach takes out her trump card.
"{Fragarach}(The Sword that Tolerates the Whole Body)!!!"
Chwahaaaaak!!!!
"Ke──────"
The launched causality-reversing blade, a divine blade that travels back in time, pierces his spiritual core. And the Gáe Bolg Alternative fired by Scáthach shatters not Fergus, but the Greater Grail.
Thud...!
Soon, Fergus falls from the sky. Because of Fragarach, the Caladbolg he launched was nullified and disappeared.
"Huh, why...."
"... It's a relic left by Connla's descendant. The trump card weapon this child received from the overseer."
"......"
A relic of Bazett Fraga McRemitz. A Noble Phantasm made with a method passed down through generations, left by Bazett, a distant descendant of Connla and heir of the Red Branch Knights.
"Across time, across a bloodline that is now almost nonexistent, I have stopped you, Fergus."
"....."
`Manannán gave it to you?`
`Yes... he said since I had a hard time because of Cú Chulainn, he gave it to me. Originally, he intended to give it to Your Majesty, but he said you refused?`
`I dislike being indebted to gods. I thought it was even since it was my nephew's transgression... So Connla finally has a divine construct too?`
`Actually, he only gave me the manufacturing method, so I have to make it from now on.`
`I see~ That's noble. Will you pass it down through the generations?`
`Yes. For generations in the family, I wish for it to be passed to a descendant of Ulster even in the distant future where my bloodline is almost gone. Because it is also proof of being acknowledged by a god.`
"To think a descendant of the already dead Ulster would plunge a sword into my chest..."
"... It's all over, Fergus. That boy will likely be saved by the girl who is the practitioner of the Third Magic too. It's all over."
"It's over.... Indeed."
It was over. Fergus's fight, his wish, had ended.
"... I'm sorry."
"For what?"
"... Everything. For leaving you alone... for making things hard for you even after death.... Everything, everything.... I'm sorry."
Fergus lies fallen, shedding tears. Even with his chest pierced, Fergus's tenacious life force allows him to at least speak. Even with his spiritual core pierced, his miraculous life force for continuing combat kept him alive.
"I do not resent you."
"I tarnished the name of Ulster. I tarnished your faces.... I sacrificed innocent people... for my own happiness, for my own peace of mind."
"You can atone for that by saving more people."
"... Why, why don't you resent me. You, because of me, couldn't die."
"Fergus... you thinking that way is only because you cannot forgive yourself."
Scáthach kneels beside him and tightly grasps Fergus's hand.
"Fergus. We do not resent you. Even if you did anything, we would not hate you. We are not disappointed... we were happy because you existed. So... please, forgive yourself now."
"...."
Kugugugugugu...!
Due to the previous battle, the cave was gradually collapsing. And from Scáthach's body, a light slowly began to rise.
"Is this the limit..."
"... Go."
"Fergus. But..."
"I'll just stay here alone. I can't... let you see me die again."
"....."
Scáthach glances at a corner of the cave, then nods and rises from her spot.
"Fergus. There's much I want to say, but I'll say just one more thing."
"..."
"I was the one who was sorry for giving you sorrow."
"... Ha. Aren't we a married couple."
"Heh..."
Scáthach takes the others and escapes the collapsing cave.
Left alone, Fergus. He sighs at his tenacious life force and gazes at the moonlight visible through the cracks of the collapsing ceiling.
".... I'm really the worst, aren't I."
"It seems so. Seeing that you failed and ended up here, it does seem that way."
"... You, why didn't you go."
Medusa comes and sits next to Fergus. She smiles faintly as if it's nothing.
"It would be lonely alone. And, I am your Servant, am I not, Master?"
"... Ha. Your Master is Sakura now, isn't she? Shouldn't you be guarding Sakura... I'm sorry. For involving you in dirty deeds too."
"What are you talking about. I was a monster who killed many people in life. There's no particular problem, right?"
"Is that so.... You crazy woman."
"Heh, you meant that just now, didn't you?"
"Yeah, there's no problem... You did it to protect your sisters, and it was because of a goddess's curse... Where were you bad? Why are you deliberately doing bad things this time?"
"I couldn't just leave you be. Someone like you..."
"I see... Do you like me?"
"Yes."
"... If Scáthach were here, you'd be dead now."
"That sounds fun."
"You're not sane... Well, there were no sane people among those who liked a lunatic like me... Medusa, you... by any chance, would you like to atone for sins with me someday?"
"Atoning for sins... That sounds good."
"Then, is that a promise? And... if, you go crazy like me, then I'll stop you."
"Is that a promise?"
"I'm bad at keeping them, but... I'll keep this one... Thank you. For staying with me...."
Fergus's breath stops, and Medusa watches over him. And as the cave collapses, the two conclude their story along with the collapsing cave.
The incident caused by one man's guilt and selfishness thus came to an end. While thinking that he wished to atone for his sins someday...
"A dark history is a past you want to erase..."
In front of a building in a certain village. A boy leaning against the wall, waiting for someone, sighs as he thinks about his past. He was utterly dismayed by the summons caused by the mistakes committed by himself, yet not himself.
Creeeak~
Soon, the building door opens and the boy's companions come out.
"Did you wait long? There was a lot of luggage to pack..."
"No, it's fine. But, is that luggage homework?"
"Well, being a student and all... Haha. Well, shall we go? Ruler."
"Yes, let's depart, Ruler. To Tours."
That was the beginning of another journey for the boy to atone for the sins of another himself.