Akira was already inside the lab.
He laid out every handwritten note he had brought back from the Demon Slayer world, the ones compiled alongside Shinobu, Tamayo, and Yushiro. One by one, he spread them across the worktable as a holographic scanner activated above them, light sweeping across each page.
Data streamed upward as the system converted the fragile ink-and-paper records into a fully digitized archive.
"Let's digitize everything properly," he muttered.
Once the backups were complete, Akira placed the Blue Spider Lily and its refined extract into the analyzer. The machine hummed softly as streams of information flooded the display.
He skimmed through the results.
Then frowned.
"…What the hell is a plant like this doing in that world?" he muttered. "This thing is way more dangerous than I thought… but I can get better potions than before."
Back then, he'd been limited to Taishō-era tools, crude equipment, diluted extracts, and trial-and-error chemistry. The results had worked, barely, but they'd been inefficient, unstable, and dangerous.
This time was different.
"No more diluted junk," Akira said quietly. "Let's do it properly."
He straightened.
"It's time for full experimentation."
Test 1:
Lycoris Caerulea Potion – Prototype 1
Akira retrieved a blood sample from the reserves he'd taken from Erika's room, properly labeled, stabilized, and isolated. Every variable had been accounted for.
"One drop," he said calmly.
The droplet touched the blood.
For half a second, nothing happened.
Then.
"…Are red blood cells dividing?"
The sample expanded rapidly, its volume doubling, then tripling in seconds.
"No… wait," Akira said, eyes narrowing. "That's not division. That's…"
The container detonated.
Akira snapped his fingers instantly. A containment barrier slammed into place, absorbing the blast just before it could tear through the lab.
Silence followed.
Slowly, Akira stared at the splattered residue coating the barrier.
"…Okay," he muttered.
After a brief pause, he added, "Next time, maximum containment from the start."
He marked the result.
LC-P.1 — Failed.
Test 2:
LC-P.2 — Prototype
This time, Akira prepared properly.
Reinforced containment and proper explosion countermeasures
Nothing will affect him now, probably.
"One drop."
The blood darkened the instant the extract touched it.
Then it hissed.
Akira frowned. "…Corrosive? Overstimulated metabolism? Extreme pH imbalance?"
The sample burned straight through the table.
Metal screamed as it dissolved, sizzling violently as the reaction ate through the reinforced surface and into the flooring below.
Akira leaned over the smoking hole and peered down.
"…I mean," he said thoughtfully, "this could be weaponized."
He straightened.
"But not really impressive."
With a sigh, he added, "Next time, we're using a better table."
LC-P.2 — terminated.
The table was promptly replaced.
Test 3:
LC-P.3 — Prototype
This time, Akira switched to a fully sealed, transparent containment cylinder.
"Alright," he said calmly. "Let's behave this time."
"One drop."
The blood didn't expand.
It didn't corrode.
It moved.
A thick, gelatinous mass pressed against the glass, slowly crawling upward. Tendrils formed, reaching out toward him like some kind of living slime.
Akira stared.
"…Why are you mobile?"
The mass shifted again.
Akira narrowed his eyes. "What in the red Rimuru Tempest are you?"
As if responding, the slime altered its shape, briefly resembling Rimuru's form.
Akira's eyes sharpened. "…How did you do that?"
He paused.
"…Wait. Are you responding to my thoughts?"
He focused slightly, imagining a spike.
The slime twitched, then a rough protrusion formed where he'd imagined it.
He thought of a flat surface.
The protrusion smoothed.
Akira's breathing slowed.
"…You're responding to intent."
He tested again.
A cube.
A sphere.
A thin, blade-like edge.
Each time, the hemal mass adjusted, slowly, imperfectly, but undeniably reacting to his thoughts.
"…Interesting," Akira said quietly.
He paused.
"Extremely weird. But interesting."
Scans flickered across the screen as he observed its structure.
No organs.
No nervous system.
No true differentiation.
"It's definitely multicellular," Akira muttered, "but why is it acting like a single-celled organism?"
He tilted his head.
"…Somewhere between a virus and an amoeba."
A hemal pseudo-organism.
"Is this even alive…?"
He sealed the container carefully and applied a label.
Specimen B-03
Designation: Hemal Slime
Classification: Reactive Pseudo-Organism
Note: DO NOT THINK AT IT.
Stepping back, Akira exhaled.
"…I'll analyze you later."
LC-P.3 — Pending further study.
Test 4:
LC-P.4 — Prototype
This time, Akira didn't bother hoping.
"One drop."
The blood convulsed.
Cells fused, reorganized, and multiplied with terrifying efficiency. The mass slammed against the containment field again and again, as if reacting to him…wanting to attack him.
Akira's eyes widened.
"…That's a self-organizing hemal supercell."
He pulled up the scan data rapidly, fingers flying across the interface.
"Each cell is autonomous," he muttered, "but linked through some kind of resonance… a distributed intent network."
He went still.
Then, experimentally, he fed it a chicken leg.
The mass dissolved it instantly, bone, flesh, everything, then its volume increased visibly.
Akira stared.
"…This is basically a Flood supercell."
His eyes sparkled with genuine awe.
"It's so cool."
The thing slammed into the containment field again and again, making it shudder violently.
Right on cue, Selena's presence flared behind him.
She teleported in without warning.
"…Brother."
Akira jumped slightly and turned around. "Sis…what are you doing here?"
Selena stood at the lab entrance, staring at the violently shifting mass inside the container.
"I came to check on you," she said calmly. Then paused. "…What is that?"
Akira gestured proudly. "Oh, it's nothing. I was just working on a Blue Spider Lily healing potion."
Selena looked at him.
Then she looked back at the thing, trying to break free from the containment.
She spoke slowly. "…Why is your healing potion so aggressive?"
Akira corrected her. "That's not the potion. That's the blood I tested the healing potion on."
He added enthusiastically, "It turned the blood into some kind of Flood supercell. Isn't it cool?"
Selena pinched the bridge of her nose.
"…Are you trying to destroy the world?"
Akira answered honestly. "No. I'm just trying to make a healing potion."
Selena stared at him. "How does a healing potion turn into an apocalypse bioweapon?"
Akira shrugged slightly. "Well, what can I say. The path to hell is paved with good intentions…"
She looked at him without saying anything.
Akira coughed. "…Fine. I might've gotten a little carried away. Sorry about that."
Selena said flatly, "Destroy it."
Akira hesitated. "But Sis… the data…"
"Do it."
"…Fine."
He raised his hand, magic flaring briefly, and incinerated the container and its contents completely. Nothing remained, not even ashes or residue.
Selena nodded once. "So, is a normal healing potion not possible?"
Akira replied, "No, it is. I already found a way to make it. I just wanted to see what would happen if the mutation continued."
Selena said calmly, "Brother. Next time you try to do something like that without telling me, I will teleport a huge swarm of cockroaches into your room while you're sleeping."
Akira recoiled in horror. "What kind of monster are you?! That's too far!"
"Then behave."
She said and turned to leave, then paused.
"…What's that?"
She pointed toward a sealed container resting on a side table.
Akira lunged instantly. "No! He's innocent! I won't let you destroy him!"
Selena blinked. "…What?"
Akira said firmly, "That's Specimen B-03. He's harmless."
Selena glanced at the label. "…Why is it labelled DO NOT THINK AT IT?"
Akira replied, "He's shy. And… some other things."
"…Brother."
"I'm keeping him."
A long silence followed.
Selena sighed. "…Fine. But remember, if it does anything, I will teleport a swarm of centipedes along with the cockroaches."
She turned and left.
LC-P.4 — terminated.
Reason: too dangerous to be left alive.
Hours later, with his focus fully restored and with no more apocalypse-tier deviations allowed, Akira finalized the formula.
LC-P.5 — Prototype (LC-α)
Controlled regeneration.
No autonomy.
No mutation.
Pure restorative response.
He watched as the scanner completed its analysis, lines of data stabilizing at last.
Designation: LC-α
Common Name: Cerulean Dew
Status: Alpha-stage viable healing compound
Akira leaned back in his chair.
"…Finally."
He wasn't done yet. But for the first time that night, he had something that could actually be called a healing potion.
He fed the refined solution into the synthesizer, instructing it to produce a small batch, vials only. Prototypes. It would take time.
When the process finished, Akira exhaled in relief.
The best part?
He hadn't started an apocalypse.
He glanced at the clock.
4:00 a.m.
Akira muttered to no one in particular, "…Well, it's already this late. Or is it early morning?"
He shrugged slightly.
"Anyway, too late to sleep. Guess there's no point stopping now."
Reaching into his inventory, he took out the red kyber crystal he'd bought earlier.
Then, another object appeared in his hand.
A finished lightsaber hilt.
It was familiar. Unmistakable.
A black grip. Familiar proportions. A design clearly inspired by Darth Vader's Lightsaber, but probably far more dangerous.
He'd created it long ago, mostly based on his own design. The only thing that had stopped him from completing it was the lack of a proper Kyber crystal alternative.
Now, that problem was solved.
Akira stared at the hilt, excitement shining in his eyes.
"…I've waited a long time for this."
He exhaled slowly, then added almost casually, "But I still need to calibrate it. This one runs on a palladium-core arc reactor, not a diatium power cell."
He paused.
"If I mess it up, it'll explode. Probably."
Then he reached into his inventory again.
This time, a large transparent containment case appeared, landing softly on the lab floor.
Inside rested a familiar piece of equipment.
Jet-black armor.
Akira looked at it and said quietly, "…It's time to finish this, too."
And then, perhaps because it was nearly dawn, or because exhaustion had finally caught up to him, or just in excitement, Akira let out an unmistakably evil laugh.
"Hahahahaha."
The sound echoed through the quiet lab.