Hero Syndrome, Vol. 1 (light novel) — Rei Ayatsuki

Heroes bristle with the power that can protect and save everyone, and these young men and women battle monsters in their dreams, doing their glorious Goddess’s bidding. …Never realizing that the monsters they fight are actually humans. Infested by the mysterious being known simply as the Goddess and transformed into unthinking creatures of havoc and slaughter, these heroes of destruction wage an endless war of blind justice. Only Charon, an elite unit led by a young man known as Azuma, stand a chance against these terrifying enemies. So what might happen when a young scientist named Kaguya who joins their ranks wants to save the heroes rather than defeat them...?