Whether it was due to his eagerness to show off his results or something else entirely, Dr. Banner's steps were noticeably lighter than usual.
It didn't take long for him to lead Eren into the lab.
He casually picked up a white lab mouse and made a long incision on its body with a scalpel.
After inflicting the wound, Banner secured the injured mouse onto a specialized apparatus.
Then, he pulled out a bottle of brown liquid and slowly poured it into the transparent chamber.
Once the liquid submerged the wounded part of the mouse—leaving only its head exposed to the air—Banner stopped.
Holding up the bottle, he began explaining to Eren:
"This is Formula No. 3. I developed it by refining the proportions from the original healing wax formula."
"No. 3 greatly enhances the healing effect and significantly speeds up wound recovery."
"Compared to the original formula, this one improves effectiveness by 0.3 times and healing speed by 0.5 times."
While he spoke, he gestured toward the mouse in the chamber.
"A wound of this severity would normally take at least three days to begin healing naturally—and two weeks to fully recover. And that's assuming no infection."
"But with Formula No. 3, the entire process—from regeneration to scabbing and even shedding—will complete in just one hour."
"If we scale this to humans, this would be the most powerful wound-healing medication ever developed."
As Banner explained, Eren could vaguely see the changes through the fluid-filled chamber—though the liquid's color made it hard to discern.
Activating his Spirit Vision, Eren's eyes darkened.
Now, everything became crystal clear.
Beneath the surface, where the scalpel had torn flesh apart, small buds of flesh were beginning to sprout.
These budding tissues wriggled toward one another from opposite sides of the wound—entwining and pulling the muscle fibers together until they fused.
While the speed didn't quite compare to his own Holy Light Healing, it was leagues faster than natural recovery.
After analyzing the effect, Eren nodded at Banner.
"You're right. This formula might just be humanity's strongest wound salve. Congratulations, Dr. Banner. You've created something that could be a lifesaver for countless people."
But Banner simply shook his head.
"This isn't my invention. I merely optimized the formula you provided. The true genius is the one who originally conceived this recipe."
"Although... I do find it strange. That person was clearly a visionary, yet oddly careless in their dosage precision. Just a few small adjustments would've improved the effectiveness significantly."
Banner's brow furrowed slightly in confusion.
Eren, however, wasn't surprised in the least.
"That's the limit of their era. The original formula was made by an alchemist hundreds of years ago. They simply didn't have the tools to be as precise as we can today."
"I see... That makes sense."
Finally understanding, Banner relaxed.
······
After letting Eren observe the effects of Formula No. 3 for a while, Banner went on to demonstrate two other optimized variants:
Formula No. 17 and Formula No. 66.
No. 17 was a specialized refinement of the original—focusing heavily on enhancing the salve's effectiveness.
While the healing speed didn't increase much, it could now rapidly treat even life-threatening injuries like evisceration. Its healing power had more than doubled.
No. 66, on the other hand, was the "civilian" or cost-effective version.
It wasn't as effective as the original, but it replaced rare and expensive ingredients with common substitutes, making it far more practical for mass production.
Its effectiveness dropped only slightly, but it was affordable and accessible—unlike the precious, limited original.
······
After going over all three, Banner seemed to remember something and grabbed a tube of thick paste from the side, handing it to Eren.
"Oh right—I almost forgot this."
"This is a byproduct from the healing wax production. It doesn't do much for wounds, but it's excellent for repairing skin tissue. When applied topically, it helps remove scars and rejuvenate skin—making it smoother and more refined."
"I thought it might be useful, so I separated and preserved it."
"Oh?" Eren's eyes lit up. "How much of this byproduct do you get?"
Banner thought for a moment. "Quite a bit, actually. The ratios vary by formula. No. 3 and 17 produce better-quality residue, but No. 66 produces the most—even if it's less effective."
"I see..."
Eren paused for a moment, then said firmly, "Banner, from now on, I want you to collect this residue separately. Start tracking data on it. I have a hunch… this stuff might be more valuable than either of us realizes."
Eren's thoughts had instantly jumped to the beauty industry.
In his past life, skin-care products with far inferior effects were already selling for absurd prices globally.
If he could package this salve residue into a scar-removing, skin-enhancing cream…
Wouldn't it become a global sensation?
Wouldn't it become wildly popular with women everywhere?
He couldn't help but grow even more curious.
Though Banner didn't quite understand why Eren was so interested in this "byproduct," he was focused on the science. Orders were orders.
"I understand. I'll gather data and compile a full report."
"No rush," Eren replied with a smile. "You look like you haven't slept in days. Go get some rest first."
Banner started to object—
But Eren cut him off.
"Long-term sleep deprivation isn't good for your control over the Hulk. And if I'm right, you haven't really slept well in ages. That's not going to help you master that power inside you."
As he spoke—
Eren's right hand lit up with a warm, milky-white glow.
Before Banner could react, he pressed it to the doctor's chest.
Thanks to prior experiences with Joker Eren, Banner had already begun to integrate Hulk's instinctual perception. And he could "feel" that this energy posed no threat—in fact, it was quite comforting.
So he didn't resist.
As the light entered him—
A warm current surged through his body.
Every pore opened as if basking in spring sunshine.
His body, worn down by countless nights of lost sleep, instantly relaxed.
That relaxation revealed a tidal wave of exhaustion hidden beneath his adrenaline-fueled research obsession.
That exhaustion threatened to erode even his tenuous control over Hulk's power.
Eren had seen that and used a basic Holy Light Heal to calm both body and mind.
As his muscles loosened, and his eyelids drooped—
Banner exhaled deeply and said sincerely, "Thank you."
Thanks to Harlem, he wasn't shocked by Eren's abilities.
"Don't be so formal. We're on the same side."
Waving his hand, Eren added, "Let's call it a day. Go get some sleep. You're clearly running on fumes."
The overwhelming exhaustion left Banner in no mood to argue.
As he watched Eren and Bucky leave—
He quietly slipped into a nearby bedroom prepared just for him.
Still in his lab coat—
He fell face-first into the bed.
Soon…
His deep snoring filled the room.
······················
Leaving the lab—
Eren and Bucky made their way to the penthouse office.
Once inside—
Eren turned and asked, "I know he's already given you the Witch potion. But have you really decided to go through with it? Once you take it, your body and soul will transform completely. There's no turning back. You will become a Witch in every sense."
"This path is irreversible."
Bucky stood in silence for a moment.
Then he replied:
"After the boss told me about the potion's side effects, I spent a lot of time thinking. At first… I was angry. The idea of becoming a woman felt like a complete betrayal of myself."
"But now… I think it's fitting."
"Maybe this is the punishment I deserve. Maybe only by abandoning who I once was can I atone for my past sins."
"Maybe only then… will I feel worthy to face Steve again."
Eren said nothing for a long moment.
Finally, he nodded.
"I respect your choice."
"If this is the path you've chosen…"
"Then let me help you remove the last knot in your heart."
(End of Chapter)
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