immune to healing

She cast the healing spell in the blink of an eye.
Faint, dim orbs of light floated up from Kamijou’s limp, unmoving body. The green glow
was reminiscent of fireflies. The lights squeezed into the gaps in his skin, burying
themselves in the tears.
But...
Then she heard a shattering noise.
The healing magic she’d just built vanished without a trace, blown to smithereens.
The cause was clear.
“...Ah...”
With unsteady movements, she looked away from his face to the right hand hanging at
his side.

His right hand.
The Imagine Breaker.
The unique power that nullified all unnatural phenomena, whether good or evil.
“Uwaaaaaaaaaaaaaahhhhhhhhhhhhhhhhhhhhhhhhh!!”
Itsuwa screamed and rebuilt the once-destroyed healing spell. But it was futile. As soon
as she cast it, the magic was broken—and again she built it, and again it was destroyed.
Though she was using necessities you could find anywhere, if she kept wasting them like
this, it wouldn’t be long before she ran out. The next thing she knew, there was nothing
left to use for the spell.

- Toaru Majutsu no Index Volume 16, Chapter 1 Part 12