It was a space utterly divorced from everything in the world.

A sealed world with no door to reach it, no exit to leave it. The noise of the city, the presence of other people--all of it was absent. No, absent was the wrong word. Severed was more like it.

Arcane Domain: Hermit's Chamber.

Hidden within the castle of the world's greatest military city, The Hegemon City Elmekia, this place served as a contemplation room for three sages. No one who might disturb their research could enter, and every scrap of noise that might disrupt their thoughts had been stripped away.

"Dreary as ever in here."

Casadine, Rank Two of Elmekia Dusk--the Heretic Knight--surveyed the pitch-black space and remarked with a note of boredom.

"If you're going to call yourselves sages, you could at least put some books in here."

To that--

"You mean bookshelves and volumes like a library?"

"Unnecessary. We've already memorized every piece of knowledge we could want."

"We are researchers. We have no need for the past knowledge found in books. Don't you think the pursuit of the truly unknown is our real calling?"

The voice of the man called Resdin, measured and brimming with intellect.

The voice of the old man called Ghislem, hoarse and dry.

And the voice of the woman called Nina, alluring and bewitching.

Three distinct voices echoed from beyond the darkness, where black steles inscribed with an unknown script stood.

The Three Sages of the Epitaph--citizens of the Divine City Sieramiris, which had thrived in an age long past. Researchers of the ancient summoning arts.

Though what loomed before Casadine were not the researchers themselves, but O-PARTS that faithfully reproduced their thoughts and summoned them through the ancient summoning arts.

"And congratulations. So you've finally been promoted to Rank Two."

"...You've been spying on the royal house's movements as well?"

"'Spying' is such a harsh word. We are simply observing the world with great enthusiasm."

"It saves us the trouble of explaining, doesn't it?"

"Then you can spare me the explanation of why I'm here as well."

Casadine fired back at Nina's silky tone with a provocative edge of his own.

"You lot must already know what happened in the Underworld."

"You mean the seizure of the Seals?"

The researcher's voice held an unusual note of resolve.

"I see. Within expectations, but we'll need to accelerate the plan. Now that the Seals have fallen into their hands, there's no time to waste."

"We shall bestow upon you the location of the Isle of the End."

"Elmekia Dusk--you will claim the Encore."

"You don't need to tell me."

Casadine gave a cold nod, his gaze as emotionless as ice.

"But what about the Silent Agency? If what you've told us is true, prying the Seals from them won't be easy."

"No issue there."

"As we said. That is what the Eidos are for."

"Our long-cherished wish will finally be realized. How thrilling."

The voices born from the three steles trembled faintly.

As though three living people were shaking with laughter.

"On that note."

Rank Two turned around.

His gaze was not directed at the laughing sages, but at the young man standing behind him.

"The extermination of 'the shining ones.' You'll be deployed."

"Yes."

The white-haired young man nodded without hesitation.

Flanked by his Eidos, Ouga--Zelbright's replacement as the new Rank One, the Wicked Swordsman--answered with a hollow smile.

"I'm looking forward to it."

Starlight.

Lying atop a dune of white sand, the first thing Dan saw was a sky blanketed with stars.

(...Night?)

(...But where is this? I was... I was just in the Demon King's Palace...)

"We're on Earth."

A girl's hand--Misty's--gently touched his cheek as he lay on his back.

Neither cold nor warm. A strange, indescribable touch.

"The coordinates drifted slightly from the Vanessa Wetlands, but it's no problem. Once morning comes, we can go pick up Rin and Silk."

"Wait--hey, what about the people in the Underworld!?"

He scrambled upright, grains of sand still clinging to his back.

None of the faces from the Underworld were here. There had been a massive explosion at the Demon King's Palace, and the only ones who'd made it out were the two of them?

And he had no memory of how they'd escaped from the Underworld to here.

"Misty, what about them--"

"Boss."

"......!"

Misty clung to him, and Dan stood frozen where he was.

"Please. There isn't much time left."

The white-haired girl gazed steadily up at him.

"I want to spend the last of the time I have left with you, Rin, and Silk."

"...Misty, what the hell does that mean?"

"I won't cause trouble for Venus Light."

The girl answered with a brave smile.

"We'll drive out the 'uninvited ones' squatting in this world, and then we return to our true duty. That's all. It's the way the world is supposed to be."

"The Silent Agency's true identity... is spirits."

"That's my working theory, yeah."

The Sword Saint's voice echoed through the silent chapel.

Shion touched the statue of the winged girl with his fingertips, his eyes narrowing slightly.

"The reason I came to Canaan was to see this statue one more time. This girl with wings--so different from any spirit we know--I keep wondering why she was called the Spirit Princess."

"...I told Ren that people in ancient times probably just deified one of the old Ancienters."

The Spirit Princess's existence had never been confirmed.

The prevailing modern theory held that some ancient Ancienter had been elevated to divinity and worshipped. She remembered telling Ren as much.

But after hearing Shion's reasoning, she could say with certainty that wasn't the case.

(...My thoughts are clearing.)

(...It's like polishing a clouded mirror until it shines.)

"How embarrassing of me."

Elies let out a breath and shook her head with an exaggerated sigh.

"I've been so consumed with spreading the spirit faith that I'd forgotten to look at something this obvious."

"Did something come to mind?"

"Yes. The spirits living in this world aren't limited to the ones we know. That's what you're getting at, isn't it?"

Elies had interacted with Dragon Princess Kyelse, Archangel Fear, and former Demon King Elise many times.

Yet her spirits had never shown any sign of being bothered by them.

"If the End War catastrophe were really spirits, then Sylph and Undine should have attacked the Three Princesses on sight. And the Three Princesses would never have stood by while Ren traveled with spirits."

"Exactly. And there's one more thing that's been bothering me."

Shion pointed his index finger far to the west.

"Something that is a spirit and yet isn't. We saw it ourselves in The Hegemon City Elmekia."

"The Eidos."

"Right. When I saw the Eidos, all my hypotheses about the Silent Agency suddenly fell into place. That's why I wanted your opinion, Elies. The diversity of spirits--the theory that beyond the spirits we know, there exist spirits capable of becoming the End War catastrophe."

"...I think it's possible."

She pressed a hand to her lips in thought.

"If that's the case, then as far as we know, there are three categories of spirits. Spirits like Sylph and Undine. Then the Eidos. And finally, the catastrophe that caused the End War."

Spirits--known to be afraid of the Eidos.

Eidos--created as tools to take revenge against the End War catastrophe.

The End War catastrophe--believed to be "something" resembling spirits.

"...But if that's true, then what is this statue?"

Elies's fingers touched the dust-covered statue of the Spirit Princess.

Her name appeared in the oldest scripture of the spirit faith. Why had this girl been revered as the being who stood at the pinnacle of all spirits?

If she truly existed, then there was no reason Elies or Ren shouldn't have heard her voice.

"I'm going to reinvestigate everything from scratch. First, I want to get my hands on the Eidos research materials in The Hegemon City Elmekia. And then--"

The Sword Saint looked straight at the statue of the girl and continued.

"I'll find the Divine City Sieramiris. If the ancient summoning arts survived to the present day even in fragments, then the city itself must still exist somewhere in the world as ruins. And somewhere in those ruins, there has to be something that can unravel the Silent Agency's true identity and purpose."

"You want to find that phantom city!? You don't even know if ruins still exist!"

"If that's the path to the truth, then there's no reason to hesitate."

A gentle smile without a shred of bravado.

Elies knew it didn't come from overconfidence.

That was simply the kind of man he was.

He followed his instincts, traveled the world, investigated whatever caught his curiosity. Simply by walking his own path, he earned the admiration of people everywhere, was honored as a Sword Saint, and was now even trying to unravel the truth behind the End War itself.

What a gift from the heavens.

(...If Ren is someone who struggles desperately to join the fray of heroes...)

(...Then Shion is, without a doubt...)

A born hero.

A swordsman fated to become a Brave Hero. And precisely because he was that kind of man, it was not only humans who were drawn to him.

"I want to see it. After every last mystery has been laid bare--I want to see what kind of world is waiting on the other side."

"Shion, happy?"

"Shion happy, me happy too."

Two guardian spirits appeared at the young man's side.

The Sign of Radiance--Will-o'-Wisp.

The Sign of Gospel--Siren.

And that was not all. The two spirit swords strapped to his back answered their call, shimmering with light.

Two guardian spirits and two spirit swords.

The greatest swordsman of the modern age, beloved by four spirits, was setting out toward the truth.