"Father, you probably wish you could see this for yourself, don't you?"
Standing before the hatch, Reiko murmured softly.
Jin, watching the feed from Hourai Island, couldn't have agreed more.
"Once the hatch is open, we will wait for exactly one minute. Then, I will have you lead the way, Onee-sama."
Anne laid out the plan with clinical efficiency.
"Leave it to me."
"If it seems there is no immediate danger, we will follow you inside."
"Understood," Alectas agreed.
"We have too little information to plan further than that," Anne continued. "However, I would prefer to proceed as peacefully as possible."
No one raised an objection.
"Very well. Opening it now."
Anne operated the lever. As they had surmised, it was the manual release; the hatch slowly swung upward.
The dark opening was roughly two meters in diameter, matching the size of the hatch itself. No lights appeared to be active within.
The three of them stood back about three meters, watching for any reaction. However, nothing happened, and nothing emerged from the darkness.
"One minute has passed. I'm going in."
With Touka strapped to her back, Reiko vanished into the hole.
Two minutes went by.
"There appear to be no abnormalities so far. Let us proceed."
"Wait, what? We haven't heard a word from Reiko yet," Alectas said, sounding suspicious.
However, Reiko and Laojun were in constant contact via manacam, as were Laojun and Anne. It was only natural that the two could communicate through the tactical network.
"Onee-sama and I have our ways of staying in touch," Anne replied, leaving it at that.
Pressed for time, Alectas didn't push for details. The two of them leaped into the open hatch.
The vertical shaft dropped about five meters. A simple ladder was bolted to the side; it appeared to be an emergency access point.
"Or perhaps an air intake shaft..."
The two quickly descended the ladder, finding a corridor extending to their left and right. The interior was brightly illuminated by what appeared to be Ether Lights (AL).
They spotted Reiko further down one of the passages. That was clearly the way to their destination.
"Still... what is this place? The floors, walls, and ceiling are all made of metal..." Alectas whispered.
Anne walked toward Reiko in silence, with Alectas arriving a beat later.
"There is no sign of anyone," Reiko reported. "The magic reactions are coming from further ahead, but..."
Anne tilted her head, considering Reiko's observation. But it was Reiko's next words that truly shocked Alectas.
"This metal... I have never seen its like before."
Reiko provided the result of her Analyze after briefly touching the wall.
"What?"
"I suspect even Father is unfamiliar with this alloy."
"A metal unknown even to a Magi Craft Meister?" Alectas asked, incredulous.
"Precisely. I wonder who could have manufactured it," Anne remarked.
Almost the moment she finished her sentence, Reiko shouted.
"Stop!"
"Huh?"
Right before their eyes, a heavy door slid out from the wall, sealing the path forward. Simultaneously, the path behind them was blocked by another protruding door.
"We're trapped!"
"A door of this caliber shouldn't be difficult to breach, but..."
Just as Reiko murmured this while testing the door's surface, a yellowish-green gas began to drift down from the ceiling. Reiko's judgment was instantaneous.
"Anne! Deploy a Complete Defense Barrier around yourself and Alectas!"
Without a moment's hesitation or questioning, Anne activated the barrier. It was an absolute shield that blocked all matter—solid, liquid, and gas alike. It would certainly shut out the toxic fumes.
However, the oxygen within the barrier was finite. While it didn't affect Anne, time was of the essence for Alectas.
"It appears to be poison gas," Reiko noted after performing an Analyze on the vapor. "Without a doubt, it is chlorine gas."
Chlorine, atomic number 17, was a chemical weapon used in the First World War on Earth. It irritates the mucous membranes of the eyes and respiratory system, causing coughing and vomiting, and can lead to death via respiratory failure.
Being heavier than air, it was notoriously lethal to soldiers in trenches.
To neutralize it safely, one would need sodium thiosulfate (Na2S2O3), also known as hypo. However, they had none on hand. (Jin was familiar with hypo as a dechlorinator for aquariums, so both Reiko and Laojun possessed that knowledge as well.)
"The vents are... over there. Fireball!"
Having calmly identified the source, Reiko first melted and sealed the vents. Next, she had to deal with the chlorine already in the air.
"..."
She coordinated with Laojun to finalize a countermeasure.
"Absorb the chlorine gas into water? Understood. I'll need your help."
Following Laojun's tactical advice, Reiko awaited his support. Moments later, a massive block of ice was transported into the room.
"As expected of Laojun. First, I'll melt the ice. Heat!"
The block, roughly one cubic meter in size, melted into a pool of water. Reiko continued to raise the temperature until thick steam filled the small space.
The steam saturated the air, absorbing the chlorine gas to form a mixture of hydrochloric and hypochlorous acid. This was highly acidic.
Reiko then drew Touka and thrust the blade deep into the floor. The unknown metal of the facility offered no more resistance than cardboard against Reiko's strength and Touka’s reinforced edge.
The highly acidic water drained through the hole she had made, and before long, the air in the sealed room was harmless once more.
"They certainly don't play fair. Now, I'll open this door."
Wielding Touka, Reiko unleashed four swift strikes—two horizontal and two vertical.
The metal of the door was sliced through like paper, creating a square opening that let in a rush of fresh air.
Only then did Anne deactivate the Complete Defense Barrier. Alectas stood there in a daze, unable to fathom what had just transpired.
"They flooded the room with poison, so I had Anne protect you with a barrier while I neutralized the air," Reiko explained simply.
"I-I see... I suppose I should expect nothing less from the automata of a Magi Craft Meister..."
"At any rate, let's keep moving. We must be even more cautious."
The three of them continued down the corridor.
At the end of the passage, they found a vertical shaft with a spiral staircase leading further down.
"We have to go deeper."
Reiko scanned the area with her built-in magi-detector. While it was a simplified model, it could reliably detect the presence of mana, making it perfectly functional for close-range scouting.
"There don't seem to be any magical traps."
With that, Reiko took the lead and stepped onto the spiral stairs.
They descended only about four meters before reaching the next level. This floor was also brightly lit by Ether Lights (AL).
When nothing happened, Reiko signaled for Anne and Alectas to join her.
"Another corridor, Onee-sama."
"Yes. It seems our destination is further below."
"You mean this place goes even deeper underground?" Alectas asked.
"It appears so."
After waiting a minute to ensure no traps were triggered, the group stepped into the new hallway.
They proceeded without incident, the acidic runoff from above not reaching this level. After about fifteen meters, the corridor turned to the right.
There were no doors along the way.
"Stop."
Reiko, in the lead, held up a hand.
Further ahead, the color of the floor changed. Where it had been gray until now, it was painted a deep purple.
"I wonder what the meaning of this is."
It didn't look like a mere decoration. It was far more likely to be a boundary marking something significant.
"Onee-sama, shall we try throwing something?"
"Good idea. Here."
Reiko had the ability to process food into projectiles for testing or combat. Solidified into spheres, they served as perfect disposable tools.
She produced a ball about one centimeter in diameter and spat it out. The sphere traced a parabola and bounced onto the purple floor. The moment it made contact...
"!!"
Blue sparks arced across the floor, and the ball was instantly charred to a crisp, scattering as black soot.