The place in the underground labyrinth of the Demon King's castle was a bunker.
"Your Highness... it seems that we didn't actually enter the labyrinth."
"It does seem that way. I'm not sure if we should call it an exit, but we've definitely come straight to a place beyond the labyrinth."
Turner and Charlotte seemed to realize that this was their true destination. It couldn't be helped, since this place didn't look like a labyrinth no matter how they looked at it.
"I think the reason we arrived here is... perhaps the labyrinth only leads the Demon King to the proper place."
"Your Highness..."
Understanding the implications of those words, Turner looked at Charlotte with a sorrowful gaze.
"It seems... I am now, in effect, no different from the Demon King."
It was unclear whether the response was to me or to Charlotte.
Nevertheless, the labyrinth had a path that only the Archdemon could see, and we reached our destination without getting lost in the maze.
Charlotte placed her hand on the bunker wall, looking around.
"Considering this, it's not certain whether this space actually corresponds to the sixth floor of the Demon King's castle's underground."
If the labyrinth were truly the sixth underground floor, they could reach it just by breaking through and descending from the fifth floor.
"Although the entrance to the secret passage appeared to be a simple passage, if it functions as a dimensional gate, we might have come to a completely different space rather than the Demon King's castle."
As Turner said, there was a possibility that this place was actually very far from the Demon King's castle.
Teleportation couldn't be used in the Demon King's castle, but there was a possibility that warp gates were installed in a limited capacity.
What method it actually was, they couldn't know.
However, what was important was that if some point of the secret passage functioned as a dimensional gate, there was a fairly high probability that it would send intruders into the labyrinth and the Archdemon to the proper place.
But ultimately, the principle wasn't that important to them now.
They had arrived in the secret space of the Demon King's castle.
"A refuge, perhaps... It has that kind of feeling."
"It does seem that way."
This vast space was filled with an enormous amount of preserved food in the storage room.
There were also training equipment for magic and weapons, as well as reagents and cultivation mediums for alchemy.
I explored the bunker with a different sense of unease than Charlotte and Turner.
It was a place where one could live alone for a very long time. At the same time, there was equipment for training.
Most of the books in the library were grimoires at a glance.
Valier would have wanted to come here and would have arrived.
In the original story, Valier would have been alive. Right here in this bunker.
That fact gave off a very ominous feeling.
Demon King Valier Junior, who witnessed the destruction of Darkland, was consumed with a desire for vengeance.
Would Valier, who had once been foolish, sharpen his fangs here to exact revenge on humanity through rigorous training?
If so.
Was it not Cantus Magna nor Akasha, but Valier who caused the calamitous Gate incident?
If I were the cause of the Gate incident, what would be the meaning of everything I did?
Wouldn't it be better for the world if I did nothing at all?
But.
I couldn't know for certain.
I knew that Valier was alive during the original timeline, but there was no evidence to suggest that he caused the Gate incident.
If I do nothing, and it turns out that Cantus Magna and Akasha were the problems, the Gate incident will still occur.
But what if they were innocent? What if my meddling inadvertently caused the Gate incident?
In the original story, Valier would have been a useless fellow. That's what my body's data from back then told me.
Could someone like him, fueled by vengeance, really become a powerful magician capable of causing the Gate incident after merely two years of study? Even when my growth rate is unparalleled in speed, could Valier have grown faster than me? That seemed impossible.
My head felt like it was going to explode.
I had never been so afraid of the unknown future.
“If only the Demon King could enter this place, then the current Demon King could have entered as well,” Turner said, consumed by her own concerns, quite different from my own.
“But why he didn't come here... I don't know.”
The prepared bunker.
I couldn't come here because I didn't know about it.
“He must have decided that it was more important for the previous Demon King to survive than for himself.”
This also seemed a plausible reason.
Rather than surviving and growing stronger himself, it was better to try to resurrect the already powerful Demon King, which is why he saved Charlotte.
And so, the bunker remained in the Demon King's castle, never having welcomed the person who should have come. Charlotte examined each room as she explored the bunker.
“It doesn't seem like there are any extraordinary treasures here. It's a refuge, after all...”
There didn't seem to be any special treasures. Nevertheless, it would be reasonable to expect incredibly powerful weapons or artifacts stored here for Valier.
But then again.
If they had a very powerful artifact, they should have used it to win the war. Hiding a powerful artifact here for future use would be a tacit admission of defeat.
It was possible that there were no powerful artifacts stored here.
Since the Demon King didn't hide here, this bunker must have been meant for Valier. It was a place to buy time for Valier Junior, who wouldn't be of immediate help in battle, to grow stronger in case the Demon King was defeated.
For now, let's set aside the question of Valier's actual capabilities.
At present, I am both a Supernatural and a warrior.
If Valier is the mastermind behind the Gate incident, then he must have studied magic here.
In that case, the place I need to investigate is the library.
If there's a magic book in the library that contains information about a portal to another world...
I just need to burn that book.
Then all my tasks will be easily accomplished.
Cold sweat trickled down my body.
If this place is the root of all problems, I can end everything by burning a few books.
I won't have to deal with dangerous tasks anymore.
While Charlotte and Turner were exploring this place separately, I headed towards the library among the numerous rooms in the building.
The key was this:
If the books in the library were written in the demon language, it would be impossible for me to read them.
So, they had to be written in a common language for me to read without arousing suspicion from Turner and Charlotte.
If a language problem arises, I'll have to bear the inconvenience of coming here alone later.
"..."
The library was quite vast.
Fortunately, it was in a common language, so I could read it well enough.
Books ranging from introductory to very thick volumes were neatly arranged on the shelves.
I didn't intend to study magic.
The book I needed to find was related to another world.
And, if possible, I'd like to find a book about the magic the Demon King had cast on Charlotte. I wasn't yet sure if what happened to Charlotte was truly magic.
There were many shelves, and it would take a long time to scan all the titles of the books. If the titles didn't hint at another world, I'd have to skim through the content as well.
It would be great if I could come back here with someone knowledgeable about magic.
Harriet would be good, as well as Eleris or Lucinil.
This place is Darkland.
Soon, there could be countless magic books or secret texts known only to demons and not humans.
As I passed the introductory books, other magic books caught my eye one by one.
[Book of the Salamandra]
[On Necromancy]
[Introduction to Soul Manipulation]
Soul Manipulation.
I couldn't help but stop in front of that book.
It was a very thick book.
About Soul Manipulation.
It was a book related to the methods of dealing with souls. I didn't know whether it belonged to the general magic system or was the Demon King's secret technique.
However, if the Demon King's soul was indeed within Charlotte, then it must be related to Soul Manipulation.
I carefully took the book out.
While I wouldn't be able to understand the specific magic formulas, I could read the introduction.
[Soul Manipulation is a study of methods to deal with souls. To master it, one must first understand the concept of the soul......]
There were various discussions about what a soul was, but I couldn't understand what it meant as it was written in overly abstract language.
However, I soon reached the part I had been looking for.
[Those who have mastered the art of soul manipulation can achieve what would normally be considered impossible feats, such as dividing an indivisible soul, manipulating the soul of another, mixing souls together, turning a living person into a ghost, or extracting a soul and transplanting it into someone else.]
[However, it should be noted that a perfect understanding of the following texts is also required to perform such acts.]
"..."
Dividing a soul.
It must mean tearing apart the very soul of a being.
Mixing souls.
It implies the ability to mingle the souls of different beings.
The ancient Demon King Valier must have been a master of soul manipulation.
Demon King Valier divided his own soul and placed a part of it into Charlotte.
The magic used on Charlotte was undoubtedly derived from the field of soul manipulation.
I have not yet confirmed the existence of magic related to this world, but I have found other magical texts I needed.
I began to select, one by one, the other texts derived from the introduction to soul manipulation, written in the footnote of the preface.
There were more than six books related to soul manipulation, and their combined thickness was about three times that of an average encyclopedia.
"What... are all these?"
As I began to stack the books on a table in the common hall, Turner and Charlotte stared at them blankly.
"I think the magic used on you is this."
"!"
"Really?"
Charlotte's eyes widened as she looked at the growing stack of books, particularly the introductory text.
"Soul... manipulation?"
"Yes, it seems that even if there are no artifacts here, there are magical texts from the demon world."
In order to strengthen Valier, the library contained texts on powerful magic and other visions from the demon world.
There may not be treasure here, but the real treasure would be the magical texts in the library.
Another thought occurred to me.
If soul manipulation is a magical system unknown to humans, and if the texts in the library contain visions and forbidden arts used by the Demon King and his demonic followers.
Then we could potentially lure Cantus Magna with them.
Whether that's something we should do or not requires careful consideration.
Turner and Charlotte were not mages, but they began to read the introductory part of the preface in the introductory text I had seen.
It was clear that they were gradually feeling the same emotions I had felt.
"A magical system that deals with souls..."
Charlotte's fingertips trembled, and Turner seemed to doubt her own eyes.
Soon, Charlotte read up to the part about what one can achieve once they've mastered soul manipulation, and she clamped her mouth shut.
"I've found it... This... This is it... This was it..."
It is by no means a small amount of content.
But if anyone, be it a royal mage or otherwise, were to master soul manipulation.
Charlotte's condition could improve.
And if that happens.
Even if my true identity is revealed later on, Charlotte will not think that I had helped revive the Demon King.
"Thank you... Thank you, Reinhardt."
Charlotte trembled as she cautiously embraced me, and I hugged her back.
Charlotte would be able to recover.
However.
Having taken on the new problem of the surviving Valier, I could never be at ease.
There were no treasures in the bunker, but books far more valuable than treasures lay dormant.
Magic exclusive to Darkland, or perhaps the Demon King.
There were certainly ordinary magic books, but also books on forbidden magic and books with just the names of unknown spells. Of course, my lack of magical knowledge could be a factor.
"This is... a problem for me, but it's also a major discovery."
Charlotte judged that the true value of the bunker lay in its library, and she was right. Turner, Charlotte, and I entered the library and began browsing the magical books on the shelves.
"It would be a good idea to bring a royal magician here later. Of course... it would be inconvenient for Your Highness to return in person."
Only Charlotte could reach the bunker.
And that would be true. Not just Charlotte, but I would also be able to enter the bunker. If we were to return with an expert in magic, we would properly know the value of the magic books here.
"For now, let's just take books about soul summoning. We don't know what might happen if we release excessively dangerous magic into the world."
"Yes, Your Highness."
Charlotte's position was that, rather than recklessly collecting the magic books, we should be cautious about releasing the dangerous books on the Demon King's magic into the world.
That choice was better for me as well.
If the magic books in this library were to be moved to the royal palace in their entirety, they would slip out of my grasp. These books are important as magic itself, but they also serve as bait for potential future contact with Cantus Magna.
Just as Cantus Magna approached Antirianus because he possessed numerous forbidden spells, I could use these magic books as bait to make contact with Cantus Magna.
Therefore, it's best for the magic books, excluding those about soul summoning, to remain here.
We still don't know whether Valier is the culprit behind the gate incident.
Is it fortunate or unfortunate?
There were no magic books related to the other world, at least not those that we could identify by their titles alone.
The possibility of Valier being the cause of the gate incident was somewhat diminished.
Charlotte's expression as she browsed the bookshelves was quite tense.
"If I return to my original state, I'll never be able to come back here, right?"
"I can't say for sure... but I think that's likely the case."
If the Demon King's soul is removed, it's natural that Charlotte would no longer be able to pass through this labyrinth that only opens for the Demon King.
"Then, let's retrieve these magic books before removing the Demon King's soul from my body."
She believes she can escape the situation where her soul is being consumed.
Seeing Charlotte's expression, filled with such happiness upon finding a clue, made me feel as if, for a brief moment, all my worries had vanished.
