Upon arrival, Ganta is fitted with a lethal collar. This collar serves two purposes: tracking and tracking inmates while causing them intense pain if they break rules.
Towards the end of the episode, Ganta is nearly killed by a falling obstacle. In a desperate surge of terror and rage, he discovers he can control his own blood, hardening it into a weapon-like form. Deadman Wonderland Episode 1
Without warning, a mysterious, cloaked figure with inhuman abilities—referred to as the "Red Man"—appears outside the classroom window and slaughters everyone in the room except for Ganta. Upon arrival, Ganta is fitted with a lethal collar
This ability—the "Branch of Sin"—reveals that Ganta is not just a regular inmate, but a "Deadman". but a "Deadman".