"Earthquake!?"

  "Is it from this magic device!?"

  "Yeah. This is normal… Let's go look at the reservoir."

  I left the main control room and went to see the reservoir lake.

  …The three girls were shocked to see the scene there.

  "Incredible! It's swirling around!"

  "It's like, a tornado…"

  Both are correct, the reservoir lake is whirling hard like a tornado.

  This phenomenon occurs because the water purifier sucks up an enormous amount of water.

  This instrument is moved by mana taken from the Dragon's Vein, it wouldn't last even 1/1000 seconds if I had to use my own mana to do it.

  Even with such a large-scale apparatus at work, purifying the entirety of this lake will still take about three days.

  "Even if it's just water, at this amount it's a huge mass. The quake-like shaking is produced by it moving."

  "Anyone who gets caught up in this won't be pretty…"

  "We've got to be careful not to fall in the pond. You'd end up like that if you did."

  I point at a magic tool that's going to fall on the edge of the reservoir lake.

  That's probably a magic tool set up by demons to deal with intruders.

  That magic tool got sucked up into the center of the whirlpool while violently spinning around in three seconds flat after it fell.

  If it were a human, they probably wouldn't get out of it alive.

  …By the way, I had confirmed beforehand that the masked man was not within the range before we entered the main control room.

  He must have got out of the Source by himself.

  "…Will this whirlpool continue forever?"

  "No its operating time is set to three days, once that passes it will automatically stop. Even if the Source has a potent mana source, maintaining this forever is not feasible."

  While we were talking, several mana reactions approached.

  Neither demons nor magic combatants, they're ordinary humans.

  "Looks like someone is coming. We should get away."

  "Well, they'd send someone to see what's going on with this much noise…"

  Looks like the Waterworks Staff noticed the purification going on and came here to check.

  We should get away before they see us here.

  "Let's escape… Oh right, before that."

  I throw the demons I defeated into the reservoir passage.

  And then I wrote something on the wall behind the demons with huge letters.

  『The special disinfectant is a poison. You were deceived.』


  The imperial Waterworks Staff would surely find these writing.

  Since those people seem to think that the disinfectant was a cure for epidemic, they may be bewildered when they stop getting more from the demons.

  "Alright, it should be OK now… Let's get out for now."

  We left the Source from the back door, and made our way toward Eis Kingdom.

  The journey back was painless since we didn't need to hide from demons.

  ◇


  The next day.

  "…We were just gone for a few days yet it feels like it's been so long…"

  "Sneaking in and investigating feels so long despite being so short…"

  "We had to stop the demons on top of investigating after all."

  We're currently taking a breather in an inn in the royal capital.

  However, we can't get too relaxed.

  We still have an enemy left, Grevil.

  "We managed to stop the doll incident somehow… But we still have Grevil to beat next right? Should we learn magic that can beat this Grevil in the next three months?"

  Alma touched the subject after some time had passed in the inn.

  Normally, I would have done that indeed.

  However, it's a bit different this time.

  "Regarding that… I'm planning to go alone for this."

  "Eh!?"

  "Are we… a hindrance?"

  "You're leaving me behind!?"

  The three voiced their surprise when I told them that.

  I give them my answer.

  "No, the three of you are a big help, force-wise… but the battle this time is too dangerous. I can't guarantee your survival."

  The four of us may have been fighting together up until now.

  However, it was all because I had grasped the situation beforehand and knew we had chances.

  We know too little about the upcoming battle.

  We don't know about current strength of Grevil, Grevil's goal, nor strength of demons that are with him.

  And Grevil isn't an opponent that will let us collect the info we need from a safe spot.

  "Our battle so far were all dangerous too didn't it? We still fought despite fully knowing that!"

  "That's right! If we're a hindrance, then OK, I get it, but if not, let us go with you too!"

  "I won't die so easily!"

  "…The degree of danger in this fight is unlike anything before… Up until now, letting your guard down would result in death, but in the upcoming fight, you could die even if you never once let your guard down."

  The problem is not purely the opponent's strength.

  If the reason for 『Soil Demons'』 revival was really true, then the 『Space Monsters』 must have had some hands in the incident this time——

  If Space Monsters are really involved, just about anything can happen.

  Even the chance of a great magic cast by the 『Space Monster』 falling at this very moment and completely obliterating this planet without a trace is not out of question.

  Literally anything can happen.

  That's just how it is when it comes to 『Space Monsters』.

  In fact, even phenomena that are impossible for this world's magic such as 『Reviving the Dead』 is happening.

  In this situation, even Iris's sturdiness is not a guarantee for safety.

  It won't be a surprise at all for even Iris to find herself unable to get away.

  I can't get these three involved in such battle.

  Our opponent is Grevil, a human of ancient civilization.

  This matter should be settled by humans of ancient civilization alone.

  "I'm still going!"

  "Me too! …If it's really that dangerous, all the more reason not to let Mathi-kun and Iris go alone!"

  "Me too, me too! Besides, if the opponent whom Mathias-san can't beat is going to destroy humans, running away now would only delay our demise!"

  As such, the three won't hear listen to my heed.

  Looks like these girls fully intend to fight even if I stop them.

  The battle this time is absolutely not one I want them to participate in.

  …However, I cannot stop them either if taking part is what they truly wish.

  "…Okay I got it. I'll take you. But tell me anytime if you change your mind. I don't mind if you choose to run right before the battle."

  "Understood!"

  "Well, I'm not gonna run though!"

  "Yes, me too!"

  And thus, the four of us are going to fight Grevil.

  Now that it's come to this, I've got to give it my all to win the fight with everyone surviving.

  However, simply training for three months is just not enough at all to achieve that.

  …Guess I'll use my ace up sleeve here.