— — — — — —
"Alright, doctor, we're heading out."
After a brief round of teasing and chatter, Kazuma and the others prepared to leave. But just as he reached the door, something came to mind. He stopped, turned back.
"Doctor, one more thing. You know about our serum now."
"If word of this gets out, it's going to be annoying to deal with. I don't actually care if people know about it, but unnecessary trouble slows me down."
"So, doctor, be good. Keep your mouth shut. Otherwise, I'll just kill you."
Kazuma looked straight at Sumire Muroto as he spoke.
"Yes! I won't say a single word!"
Sumire answered immediately—and for the first time, she genuinely felt killing intent from him.
Before, just standing near him felt like standing near a sword. But now, with his killing intent released, it was like a beast had opened its jaws in front of her. The metallic scent of blood rushed toward her senses. Even someone like her, who worked with corpses every day, felt a freezing chill crawl from her tailbone all the way up her spine. Every hair on her body stood on end.
"That's good. Doctor, do you know the saying 'One moment of truth is worth a lifetime of living'?"
Kazuma glanced down at the oath-bound relic he carried. The contract was already active. Once triggered, there was no way Sumire could reveal anything.
"I do. It means if someone can understand the truth, they can die without regrets. And honestly, that's how I feel. If I could study that healing serum even for just one moment, I'd really die without regret!"
Even now, she was thinking about the serum. Truly, a mad scientist to the core.
"Nope. Wrong."
"What it means is: I already found where you live. Next time, I won't need to waste time tracking you down.... Well, maybe I said the wrong saying."
He didn't even wait for her reaction. Kazuma turned and walked out. As he left, every hallway light flickered and went dark under the pressure of the magic force he released—leaving only the dim emergency lights behind.
Sumire stared after him… and suddenly realized—
They had talked so much, yet she had never clearly seen his face.
She tried to focus on him as he walked away, just to get one glimpse. But before her eyes could adjust—everything went black. The last thing she saw was a shadowed profile as he slightly turned his head.
---
"This doctor sure is weak. She just fainted like that. And they call her the smartest person in the world? Doesn't seem that great to me."
Enju puffed her cheeks, glancing at the collapsed Sumire—mostly focusing on a certain part of her chest.
"She didn't faint from fear. She hasn't eaten in forever and got overly excited. She passed out from low blood sugar," Kazuma said.
"Should we help her? Won't she die like this?" Kayano asked quietly. She knew well what hunger felt like.
"Kayano, she has food. She just refuses to eat it. Don't worry. Let her starve a bit longer—she'll wake up on her own."
"…Idiot," Kayo muttered nearby. Though it was unclear whether she meant Sumire, Kayano, or maybe a certain someone staring at someone else's chest.
---
They returned to the outer area base. Night had already fallen.
Kazuma distributed the cure serum, lowering all of their rates down to 1%
He finally understood why the infection couldn't be completely cured—because the Gastrea virus had become part of their cells. Like cancer: harmful, but still part of the body. Remove it entirely, and the body would be destroyed.
Better to suppress it. As long as the corrosion rate stayed low, it wouldn't cause harm.
When he finished, it was time for Sailor Moon to air, so the girls all ran to the TV.
Kazuma sat outside alone, letting the evening wind pass over him, planning to drink under the moon.
"Guild Master… can I sit with you?" Kayo walked out, approached, and spoke softly.
"You can. But Sailor Moon is on right now. Aren't you afraid you'll miss it?"
It was strange—she was always the first one planted in front of the TV when it aired. Of course, she claimed she was forced by the other girls.
"No worries. I set the recorder. It's not as fun as watching with everyone, but it's fine."
She sat beside him and gently took his hand.
"Master… what the doctor said earlier wasn't wrong. But she didn't finish the explanation."
"Cursed Children are born with at least ten percent corrosion already. That's when the count begins."
"But according to the doctor's research—if the corrosion rate is pushed below ten percent, then for every one percent decrease, the rate of further corrosion slows dramatically."
"If we get it below three percent, our bodies' anti-Gastrea factors might keep up with the virus."
"It could become stable. Balanced. Meaning it wouldn't increase anymore."
"So what she said about us not living long is wrong. We can keep living."
"???"
"You… didn't think I was upset about that, did you?"
Kazuma finally understood. She thought he was drinking alone because he was grieving.
"Every time Sailor Moon airs, you sit and watch it. Even if you don't say it, I know you like it too."
"But today you walked out here alone… I thought—"
"I know you carry a lot. And you never show weakness. But… you can rely on us too."
"We're not little kids anymore. We've gotten stronger. We can help you."
Kayo was so serious. If Kazuma wasn't actually sad tonight… this was going to be incredibly embarrassing for her.
"I'm really not sad."
"I didn't even listen to what the doctor said. 'Impossible'? That word means nothing to me."
"I just do what I set my mind to. Whatever comes later—we'll deal with it then."
"As for your corrosion rates—who cares? If needed, I'll just make serum for you every day."
"I'm filthy rich. You could drink that serum like soda and I'd still be able to supply it forever."
Kazuma spoke with the calm confidence of someone who really could back it up. With the Gate of Babylon behind him, it wasn't bragging. It was just fact.
Unlike enchanted weaponry, these items only consumed magic when activated. Just pulling them out was basically free. Even duplication barely used anything. The mana cost of firing his Magical Convergent Cannon once could probably make enough serum for a whole city.
"Master… you're very sad, right?" Kayo stared at him intensely.
"I literally just told you I'm not."
"You're sad."
"I really am not."
"You're just trying to act tough?"
"What, am I obligated to be sad today?"
"Yes."
She nodded solemnly. If he didn't show at least a little sadness today, she was going to crawl into a hole and never come back out. This was simply too embarrassing otherwise.
"…Fine. I am totally very sad. Thank you for comforting me."
Kazuma sighed and reached out to rub her head. This girl's imagination could run a mile. Sometimes being too smart was its own problem. Whatever. He'd indulge her this once.
Feeling his warm hand gently ruffling her hair, Kayo relaxed with a soft, relieved expression.
"Don't worry, Master. We'll live a long, long time. According to the doctor…"
"Gastrea creatures effectively have no lifespan limit. And for us Cursed Children, if the corrosion rate issue is solved, our natural lifespan is very long too."
"We can stay with you for a very, very long time." She leaned against him, voice soft and a little spoiled.
"Honestly, I feel like I might die before all of you at this rate." Kazuma muttered. The short-lived one had become himself. So he was the side character destined for an early death now. Great.
"No. I'll invent a medicine to make you live forever."
"Oh, right. The doctor's notes mentioned a special serum that grants regeneration on par with Gastrea."
"It has a twenty percent risk of turning into a Gastrea though. But it's fine. I'll find a way to remove the side effects."
Kayo hugged him tightly. She always liked to act grown, calling herself smart and mature. But she was still just a kid who wanted someone she could rely on. Before, she only had herself. Now she had her Guild Master.
"…Yeah. I believe you. You'll be our guild's best engineer and best doctor in the future."
"Makarov would love you."
Kayo looked confused, "Makarov?
Kazuma stayed silent. He had forgotten that the old man was still the real guild leader. But well… he'd probably forgive him after seeing such cute, super talented lolis, right?
...
"Kayo, what did you mean by regeneration serum? And can you really make it?" Kazuma asked, changing the conversation.
Then, following her description, Kazuma found the regeneration serum in the Treasury. He found it quickly.
Actually, there even was an upgraded version that removed the mutation risk. Of course, the regeneration had been toned down. A normal person would heal extremely fast—though not like a Gastrea. More like "visible healing of a deep cut" level.
He decided not to tell her. Let the kid have her righteous scientist moment.
"Yes. I'll do it. I don't really like fighting or killing. Even if I'm doing it now, I still don't like it."
"I won't be the strongest fighter. I'll be the strongest scientist and doctor."
"All the weapons they use will be mine. All the medicine they rely on will be mine. I may not be the strongest, but the strongest will be made by me."
Kayo said it proudly.
"…So if they use your weapons to kill people, whose kill is that? Doesn't that bother you?" Kazuma raised an eyebrow.
"Who cares. If I don't see it, it doesn't count." She pouted stubbornly.
"…How did you end up like this?"
"Obviously you, Master. By the way, can I call you 'Onii-chan'?"
She looked up at him, eyes hopeful.
"Sure. Just don't forget to call me Master when we're working. Off hours, 'Onii-chan' is fine."
"Onii-chan!"
She wrapped him in a hug and rubbed her face against him. These children who once had no future at all were now working toward one with everything they had.
Kazuma couldn't help but smile. A cute little loli calling him "Onii-chan"—who wouldn't melt a little?
"…So, Onii-chan, what were you doing out here in the middle of the night?"
She eventually regained her usual blank expression.
"Drinking and looking at the moon. You're kids, so you can't drink. If I drank inside, you'd all beg for a taste."
"Is it good? Onii-chan, let me try." Enju popped up from nowhere.
"…I knew it. The rest of you can stop hiding. Come on, I'll let each of you taste a sip."
"Hehe~"
In an instant, every loli in a ten-meter radius jumped him.
"I want to die."
Kayo curled up in his lap, burying her face in shame. If only she had learned Haki sooner, she could've sensed them coming and prevented this embarrassment.
Once the lolis had tasted the alcohol, squealed, and were shepherded back to bed, Kazuma finally got a quiet moment.
He took out the regeneration serum.
"Stinky tofu flavor? Who in the world came up with this?"
The more he tried to convince himself not to, the more curious he became. Eventually, he couldn't resist.
He drank it.
"…Absolutely disgusting. Whoever made this has severe brain problems."
If the flavor was meant to torture, they succeeded. He felt like he just drank something scraped out of a sewer.
Still, the potion worked gently, warming his body. No pain, no dramatic transformation. Completely refined through countless experiments. The scientist who made it was definitely insane—but also a genius.
It would enhance physical recovery and improve the body overall. Even increased magic capacity. Only downside: it worked slowly, taking at least a month to complete.
"Still that researcher definitely had something wrong in their head. Who makes stinky tofu flavored medicine?!"
Even just remembering the taste made him gag.
"…Forget it. If I think about it anymore, I'll throw up."
He began browsing his Treasury again. After a bit of searching, he found something interesting.
"Floating Cannons? Magic-tech Hypergravity Floating Cannons?"
"…Guess it's time to upgrade my equipment."
He stared at the sleek mechanical spheres and instantly lost interest in the old Magical Convergent Cannon.
.
.
.