"Books?"

  "Yeah. It's books."

  I open the box.

  Inside, there's 10 books that were very familiar to me in my past life.

  "…These letters, never seen them before."

  "These books are really really thick… What letters are these?"

  Nobody in this era is capable of deciphering ancient civilizations' language.

  Probably because of demons.

  "Mathi-kun, can you read this?"

  "Yeah, I can… They're letters from an ancient civilization…"

  I open a page.

  『General Magic Textbook』 written in ancient civilization's language is on it.

  These books were the most widespread textbooks during my past life.

  They have everything from the most elementary magic to high level spells used on the front line.

  The number of pages totaling 5000 pages split into 10 volumes… and this box contains all ten volumes inside.

  …I've memorized everything in these books, so I don't need them though.

  "Eh, Mathi-kun, you can read the ancient civilization's language!?"

  "But then, you'd die from the curse…"

  In this era, this hearsay 『Those who attempt to decipher ancient civilization's words shall die by its curse』 exists, but the part 『die if you try to decipher』 may not be exactly wrong.

  Though not because of a curse.

  "…The thing that's killing people who attempted to read ancient civilization's writings were most likely demons, not a curse."

  "Demons… Ah, it was to discard chantless magic was it?"

  "Exactly."

  Those demons are afraid that people would acquire skills from the civilization such as chantless magic if they're able to read documents from those eras.

  Assassinating anyone who succeeded in deciphering such is just an obvious crisis management.

  "Which means, Mathi-kun won't have to die!"

  "I mean, could a mere curse even kill Mathi-kun… So what's in these books?"

  Alma points at the 『General Magic Textbook』.

  I turned over the pages, and confirmed that the content was identical to what I knew in the past.

  "These books lay out ways to use chantless magic and many kinds of such spells… I've memorized all the magic written in these though, so they're rather pointless."

  "All of it!? These thick books!?"

  "Yeah. I've read these books way back."

  In fact, that's not exactly correct.

  I wrote some parts of this 『General Magic Textbook』 myself.

  I did it when I was still quite young though, so there's some obsolete and wrong parts to the me now.

  "Even if you read it before, all these books…"

  "It's not at a level you can memorize… It's like Mathi-kun is Mathi-kun after all…"

  …What does 『Mathi-kun is Mathi-kun』 even mean.

  Please don't make up a new adjective on your own.

  That aside.

  "Question is, why would anyone leave these books here."

  "Isn't it for demons to read? I mean, ancient civilization magic textbook sounds super awesome!"

  Alma pointed at the magic textbook.

  But the demons probably had no clue about these books either.

  This hidden room isn't one that can be opened and closed many times.

  "The hidden door was not open when we entered this room. It only did after we got inside this room."

  "…In other words?"

  "Someone must have made this hidden door to open when a battle ensued in this room. I'll keep these with me for now."

  I put the books in Storage magic.

  The person who made this hidden space must have wanted to teach present era humans chantless magic.

  Although the textbook used by Second Royal Academy is better in regards to introducing chantless magic…


  …Wonder if someone left them here for demons to read when the time comes.

  Well, these books aren't necessarily useless, I'll just donate them to the Second Academy when we drop by next time.

  Quality of the writings may be questionable, but they still contain an abundant of magic knowledge after all.

  I went out of the hidden room while thinking that.

  There's still something we need to do here.

  "Huh, where are we going?"

  "To the Main Control Room of the Source. We're going to stop the flow of poison from the Source itself."

  The Source's water reservoir is humongous, it'll take too long for the poison to come off if we leave it as is.

  It'd be bothersome if our enemy misused the life force gathered until then, so we should purify the poison before we go back.

  "Is that possible?"

  "Yeah… With a super large-scale magic tool, its moving parts have quite a force y'know."

  I open the door to the Main Control Room that's right next to the main reservoir.

  Bookshelves and stuff inside the room have all been weathered down into crumbling shambles, but the magic tools are all fine since they were made under the assumption of long-term usage.

  This is the first time I'm going to personally control this, well I should manage somehow.

  I operate the magic tool while thinking that.

  Since I only need to simply purify the water, the procedure is not very complicated.

  Simply putting the purifier at maximum throughput should suffice.

  "Alright, here I go."

  I put the water purifier at full throttle.

  Then… Loud sounds could be heard from the walls around us.

  At the same time, the ground below us began to shake.