The place where Nereus was dragged was none other than the Black Forest.
‘Because we need to find the source of the Pond Poisoning.’
What does the word ‘poisoning’ mean? It refers to a condition in which one excessively consumes a substance or is exposed to a toxin, causing problems.
There are other meanings, of course, but in this case, Pond Poisoning referred specifically to that kind of affliction.
But then, what exactly is this Pond ‘poisoning’?
‘It’s not like it’s an epidemic or something.’
And indeed, it wasn’t. It only looked like one because the residents of the Tenus territory all shared one particular commonality.
‘The water supply.’
The people of Tenus all drew their water from the same wide lake, which branched out through channels. That lake was located deep within the Black Forest, which is why it wasn’t well known.
“Wow, it’s really dark here. So, why exactly are we here?”
“Because of the deal with Lady Ekati. To treat a disease properly, we need to understand its exact cause.”
The lord of Terminus probably believed the cause to be something else.
Since most illnesses begin like a common cold, they were likely researching treatments based on those kinds of symptoms.
‘Well, coughing is one of the symptoms of Pond Poisoning, after all.’
“So how do you plan on finding the source?”
“I think the water in Tenus is the problem.”
“And how do you know that?”
“I got access to some data from the Terminus estate. I looked at the order in which people got sick and the characteristics they shared. It was mostly the elderly and frail children. That usually means they’ve been exposed to something over a long period, or they didn’t have any antibodies when first exposed…”
“H-Huh? Antibodies? What’s that?”
Oh no.
At this point in history, the concept of antibodies didn’t exist yet. I quickly shut my mouth.
‘Was it supposed to be discovered within the next two years?’
I always get confused about the timeline of these discoveries.
“Uh… Well, Dad doesn’t really need to know.”
“You’re treating me like a fool again, aren’t you?”
“Maybe sometimes I did, but… this really is something you don’t need to know.”
Watching Nereus grumble at my comment, I couldn’t help but laugh. Talking to him lightened the weight I’d felt moments earlier.
‘Still, I don’t get why I’m feeling so heavy-hearted like this.’
“So, clever Lala. If the water’s the problem, you’d need to find the water source. Did you ask the lord of Tenus where it is?”
“Huh? No?”
“Why not?”
“Why would I ask that?”
If I asked, the lord of Terminus would instantly understand what I was implying.
She might not be active in high society, but she’s still the head of the 6th noble house. Even just before we came here, she proved she’s not someone to be taken lightly.
‘If she were so foolish as to not pick up on my intent from those words, this territory would have already fallen to ruin.’
She would realize that the lake is the source of the current illness.
‘I’ll tell her eventually—but not now.’
The source of the disease would later be discovered by a member of Wita while restoring the fallen Tenus territory.
The record only states that it was ‘deep within the Black Forest.’
But…
‘With this, I can find it.’
I took out a vial containing Mermaid’s Tear.
I had packed it just in case—partly as an emergency reserve, but also as part of the deal I’d made with the head of the Terminus house.
Mermaid’s Tear looked like a pearl but emitted a faint glow.
More importantly, this glow wasn’t just for beauty’s sake.
The light grew stronger the closer it got to water.
It wasn’t dazzling, just a subtle difference—so until now, it hadn’t been all that useful. But in the future, a drug would be developed that enhances this trait.
It was actually a byproduct of another treatment drug.
Thanks to that, I—who had held a doctor’s license at the time—was able to learn about it.
‘I made plenty just in case, so even if I need it again later, I won’t have to worry.’
It might seem like embezzlement, but I’m currently the only person who can cure Pond Poisoning anyway, so…
‘Even if the Terminus lords figured it out, I’m sure they’d pretend not to know.’
“This medicine amplifies the light from Mermaid’s Tear.”
“How do you come up with stuff like this? Wow, kids these days have incredible imagination~”
It had nothing to do with imagination, of course.
But I kept my mouth shut to preserve Nereus’s illusion and innocence.
“Anyway! Just follow the light.”
“Alright, alright. Looks like it’s that way.”
As we pushed through the bushes, the glowing steadily intensified.
It got tough halfway through, so I asked Nereus to carry me.
“…It’s here.”
After walking for quite a while, a cave entrance finally revealed itself.
I tugged on Nereus’s clothes, urging him to go inside.
Step by step, we entered the cave.
At some point, a soft light started emanating from deep within.
Even Nereus widened his eyes, sensing the strange sight.
“Are those glowstones?”
The inner walls of the cave, surrounding a vast and deep lake that served as the water source, were encrusted with sparkling glowstones.
“Wow… I wonder how much this would be worth?”
The glowstones here were a type of raw mineral that never stopped emitting light.
Moreover, they didn’t spread fires during accidents, nor did they require supplementary energy like magic stones—making them a favorite among many.
‘Sure, there’s the downside that you can’t turn them off, but just cover them with cloth. They’re practically semi-permanent—that’s why people like them.’
“This is a glowstone cave.”
Nereus muttered as he looked up at the glowing stalactites hanging from the ceiling.
Even if you chipped them off, you’d never fully remove all of them.
And that was the problem.
There wasn’t yet a definitive study, but the concept of microorganisms would be made public in a few years.
Thanks to that, medicine would start to categorize diseases more precisely and advance rapidly.
‘Anyway, how advanced future medicine becomes isn’t the point right now.’
Inside these glowstones lived microorganisms.
They weren’t harmful to the human body upon contact—but in water, they slowly dissolved and released weak toxins.
Until now, there hadn’t been much of an issue because the toxins were so faint.
But now they had accumulated.
Water wasn’t just for drinking—it’s used in daily life for cooking, washing, and more. Over time, these residual toxins had seeped into the ground, homes, clothing, food…
‘That’s why the elderly were the first to show symptoms—then the children, who lacked immunity.’
“Dad, can you chip off a bit of these glowstones for me?”
I asked Nereus to collect some glowstone samples while I scooped water from the lakeside.
To the naked eye, the water looked perfectly clean.
‘Now I just need a few days to work on this.’
Since this required delicate handling, I had to examine everything with painstaking detail.
I wasn’t sure how long this fragile body of mine could hold up—but still…
‘I decided to do this, so I have to see it through.’
A little exhaustion would be worth the valuable results.
And while I didn’t want to imagine failure—if I did fail, my family would die too.
“Let’s head back for now—cough!”
“Huh? Why are you coughing all of a sudden? Are you sick?”
“No, something just caught in my throat—cough, cough…”
My throat grew drier by the second, pain creeping in.
Cough! Cough! Cough!!
“L-Lala?! Wait—what’s wrong with your face?! Why are you so pale all of a sudden?!”
‘Wait…’
Through my blurry vision, I looked at my fingertips.
They were already turning black.
‘Damn it…’
It was Pond Poisoning.
It occurs in about one in every 5,000 infected people.
And now, I was experiencing a sudden seizure-type onset of it.
My tongue stiffened rapidly inside my mouth, and the sensation in my fingertips began to dull.
The worst part about seizure-type Pond Poisoning was that its symptoms were much more severe than the typical form.
‘Especially the numbness in your senses—that’s the absolute worst.’
Even my taste and smell dulled.
There was no need to mention my vision.
At the same time, my whole body felt weak, and it was becoming hard to stay upright.
But I didn’t have the luxury to lie down and rest.
‘How long has it even been since we arrived, and I’m already like this?’
Pond Poisoning usually only triggered when the toxin accumulated beyond a threshold or in extremely vulnerable individuals like infants or the elderly.
Though I was frail, I had assumed being six years old gave me a buffer.
That had clearly been a mistake.
I pushed my sleeve firmly over my hand.
“It’s just cold in here. I’ll be fine after a short rest. You’ve mined everything, right? Let’s go.”
Now we just had to get back as quickly as possible.
There were no tools in our current era capable of extracting microorganisms from the ore, so I had to devise a way myself.
‘Since there are already medicines made from minerals, one of those methods should be close enough.’
“Polaris.”
‘—Ah.’
At some point, Nereus had crouched in front of me and was lifting my sleeve.
I’d been so caught up in thinking about what came next, I hadn’t noticed.
His gaze fell to my fingers—already turning black.
As he lifted my sleeve further, more of my skin, blotched and discolored, came into view.
“This… is this really just because you’re cold?”
“Uh…”
“I may be an idiot, but even I know this isn’t right.”
“….…”
“Why are you lying to me?”
