It was now the third day since Scorpio had come ashore in Tokyo Bay, and the fourth since Kain had arrived in this world.
Scorpio had been disposed of that first day, before Libra entered the sea.
A Varanium-containing shell had been fired straight through its body, killing it. Some of its remains had also been recovered for research.
And just as expected, Libra had stopped advancing after Scorpio's death.
Meanwhile, research into the Gastrea virus had made considerable progress.
They had now developed two types of vaccine.
Both were made using serum from the same person.
An almost undetectable substance within the hereditary factors in his blood could reverse the changes caused by the Gastrea virus.
Put simply, that substance contained information about the human genetic structure. It broke down the mutated Gastrea virus, separating it back into its original human and animal genetic components.
At the same time, the Gastrea virus itself reverted to its initial state, before it had incorporated genetic material from any animal.
For a brief period, the reset virus, human genes, and animal genes remained separate, like layers of oil and water.
The three components had to be isolated before that state ended.
Afterward, combining the original virus with human genes produced the desired result: a virus that mimicked human genes but remained in a kind of vegetative state.
They could call it the human-type Gastrea virus.
This human-type virus could then serve as a substitute for Kain's serum. A high-concentration solution could be used to convert a lower-concentration sample of the ordinary Gastrea virus, producing more human-type virus with the animal genes removed.
Mixing that human-type virus with the panacea and injecting it into an infected person would lower their corrosion rate, ultimately restoring them to a fully human state.
A healthy person only needed an injection of the human-type virus, without the panacea. It functioned as a preventive vaccine. Even if Gastrea bodily fluids entered their system afterward, they would not become infected.
However, the human-type virus itself came in two varieties.
The first was produced by combining the reset virus with human genes from someone other than the serum donor. This version could subsequently be cultured artificially.
Even when combined with the panacea, however, it could not reliably restore someone whose corrosion rate had exceeded fifty percent. Even if they still looked human and had not yet transformed, it could not stop the mutation.
The second variety used the serum donor's own human genes.
That version could not be cultured artificially.
And when it was combined with the panacea...
"What happens?"
Miori sounded nervous.
Kisara was also a little tense. The doctor before them looked positively feverish, as though the vaccine in her hand were some legendary elixir.
"Have you heard of a certain medicine in The Tale of the Bamboo Cutter? One that would drive people mad with desire?"
Sumire's eyes practically shone as she spoke.
"The elixir of immortality?"
Miori's voice went dry.
As she stared at the tiny amount of medicine in the doctor's hand, she could barely conceal the hunger in her eyes.
Anyone familiar with The Tale of the Bamboo Cutter would have heard of the medicine that granted eternal youth and immortality.
"Isn't that a little exaggerated?"
Kisara's eyes widened in disbelief.
Then again, perhaps it was not so far-fetched.
The man who had supplied the serum could survive even after having his head blown apart.
"Yes, that is an exaggeration. But as long as you're still alive and conscious, even if all that's left of you is a head, this drug can induce molecular-level regeneration. That holds true even if your corrosion rate has exceeded fifty percent. Any physical defects, any missing organs, all of it will regenerate. More importantly, afterward, your body will be immune to disease and remain in perfect health."
Even Sumire could barely contain her excitement.
It was not the effects themselves that thrilled her most.
It was the fact that she had managed to create something like this.
Beside her sat a culture vessel containing a piece of flesh.
She had cut it from her own body for use in the experiments.
Now that piece of flesh was practically the legendary taisui, an endlessly regenerating mass of living tissue.
Her gaze shifted to Kain, burning with curiosity.
That man held far too many secrets.
And those secrets went beyond his body. He could describe medical equipment far beyond anything this era should possess, along with knowledge of human genetics that exceeded their current understanding.
Only with the information he had provided had she been able to create the substance in her hand in a few short days, working almost without rest or sleep.
"That little can do all of that? And if someone gets injured again after taking it, how well would they recover?"
The person asking those detailed questions was the serum donor himself, Kain.
The vial in Sumire's hand contained less than five milliliters.
"Of course this tiny amount isn't enough. The required dose depends on the recipient's body weight. For someone of your weight, it would take roughly a hundred milliliters. As for subsequent injuries, achieving molecular-level regeneration again is simple. You just need enough nutrients. We have the panacea, don't we? Take a dose proportional to your body weight, and you can regenerate at the molecular level."
Her explanation matched some of Kain's own experiences with the panacea.
The dose required to regenerate his missing body parts at that level was almost exactly the same.
In other words, had they just created another version of the panacea?
But this method of producing it required his serum.
And considering how much he had already supplied to produce those five milliliters...
He did a quick calculation.
Making a single hundred-milliliter dose would require draining almost all the blood from his body.
Incidentally, once the human-type virus and the panacea were mixed, the liquid in her vial became transparent.
It was also extremely viscous, forming long strings, and looked remarkably like a certain bodily fluid.
The white panacea already resembled that same substance.
The similarity was almost uncanny.
"By the way, Doctor, you haven't explained what happens to the Cursed Children after they recover from the general-purpose vaccine. Would they lose their innate abilities too?"
Miori had suddenly realized that this point had not been addressed.
If the treatment turned them into completely ordinary human children, that would create another headache.
The Cursed Children were currently humanity's main fighting force against the Gastrea.
That meant not everyone would welcome the vaccine.
"What do you think? Once their genes have been restored to a fully human state and the animal factors removed, where would those abilities come from?"
Miori had more or less expected that answer.
Still, until she actually heard the doctor say it, she had held out a little hope.
So much for that.
Then another thought occurred to her.
"Doctor, the general-purpose vaccine is dosed according to body weight too, right? Could we reduce the dose and just lower their corrosion rate?"
"I was beginning to think you'd never ask."
Did that mean it was possible?
"A half dose can lower the corrosion rate. But it would be best to use it only when the rate is above ten percent. Otherwise, they could revert completely to ordinary humans. However..."
"However?"
"We'll need to administer it to actual Cursed Children and observe the results before we can be certain. So far, all our test subjects have been adults."
Developing the general-purpose vaccine over the past few days had already cost more than thirty lives.
All the subjects had been adults, D-class personnel.
They had been injected with Gastrea bodily fluids, and the progression of their corrosion had been observed at different intervals to gather data.
Sumire believed the effects should not differ too much in theory.
But the Cursed Children had carried the virus since birth.
There could still be differences in how they responded.
Just then, two phones rang.
Miori's and Kisara's.
"What? You've got to be kidding! It's only been a few days since Scorpio, and now this?!"
Miori's voice rose. She looked as though she wanted to cry but could not quite manage it.
"Oh? The plot's moving along this quickly? How interesting."
Kisara, on the other hand, sounded entertained.
She looked at Kain.
"Aldebaran's here."
There was such unmistakable delight in her voice that Kain gave her a long, searching look.
"What's that look for? I haven't sunk that low. At most, I knew something and didn't report it."
Kisara glared back at him.
She had not gone that far off the deep end.
All she had done was learn that Monolith No. 32 had a structural defect and refrain from warning anyone.
This really was a coincidence.
Tokyo Area simply enjoyed far too much attention from the "goddess of luck."
"Heh. Actually, let me correct that. Aldebaran isn't here. It's already been here and left. It probably came late on the night Scorpio was disposed of, using the sudden downpour as cover to corrode Monolith No. 32."
The heavy rain had continued for days. Only today had the weather begun to improve, allowing them to discover the serious damage to the Monolith.
Which meant they had only about three days before it collapsed.
(End of Chapter)
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