Shape corrosion is the term used in Black Bullet to define how much of the host body the Gastrea virus has taken hold. If it gets over 50%, the human turns into a Gastrea monster.

It is specially important for the Initiators, because they are infected at birth, and there is always a risk they turn into Gastrea in the middle of an operation. If an initiator is injected with more virus (by monsters, for example), shape corrosion can increase in a very short time.

During the series we learn that

Aijara Enju's Shape Corrosion is well over 40%, putting her almost on the death row, should the virus spread more.

There is special medicine all initiators have to take regularly to halt the spread of shape corrosion, but is there any method mentioned in the black bullet manga or anime of reverting this index?

  • I just looked over the wiki, and it appears to make no mention of any process to revert the index, or even a drive to find one. I've only watched the anime, and it was a while back, though I don't recall them mentioning it there either, at least as a highlight of the episode/plot. Still, I'd be surprised if there wasn't a mention somewhere of something along the lines of there is no [known] cure somewhere in either of the transcripts.
    – user9554
    Mar 26 '15 at 18:10

The corrosion rate is not reversible, it can only be inhibited

The Cursed Children were constantly taking massive doses of corrosion-inhibiting medication to control the Gastrea inside their bodies, but it still only inhibited and did not stop the corrosion completely. Because the girls carried the inhibiting gene, they did not turn into Gastrea immediately like normal people, but if they suddenly used a lot of their power, or if Gastrea bodily fluids got inside them, then their corrosion rate would slowly increase. And then, like a normal person, if their corrosion rate went above fifty percent, then the corrosion would start, and they would not be able to keep their human form any longer. There was nothing that current medical technologies could do to change that limit.

Kanzaki, Shiden. Black Bullet, Vol. 1: Those Who Would Be Gods (pp. 211-212). Yen Press. Kindle Edition.

It is also the reason why Rentaro shot Kayo

Kayo Senju could not be saved. She had to die right here, right now.

Kanzaki, Shiden. Black Bullet, Vol. 1: Those Who Would Be Gods (p. 212). Yen Press. Kindle Edition.

In a conversation between Sumire and Rentaro it is also mentioned that the Cursed Children cannot be freed from the shackles that is their corrosion rate

Rentaro shook his head slowly. "That’s impossible, Doc. I can’t think of a life without Enju and Tina anymore." "But they will fall like leaves one day. Rentaro, don’t chase after falling leaves. The lifespan of Cursed Children is bound by the shackles of the corrosion rate of their body, which they cannot be freed from."

Kanzaki, Shiden. Black Bullet, Vol. 3 (light novel): The Destruction of the World by Fire (p. 81). Yen Press. Kindle Edition.

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