Prior to the start of the story, a massive earthquake ravaged Japan's mainland and destroyed most of Tokyo, sinking three-quarters of it into the ocean. Ten years later, the story shifts to Igarashi Ganta, a seemingly ordinary, unassuming middle school student attending Nagano Prefecture's middle school. Anescapee, a survivor of the great earthquake, Ganta has no memories of the tragedy and has lived a simple, normal life. This all changes one day when a strange man covered in blood and crimson armour appears, floating, out of his classroom windows. Smirking madly, this Red Man massacres Ganta's entire class and, instead of killing him, embeds a red crystal shard in his chest. Within days of the massacre, Ganta is declared the sole suspect and, following a suspiciously quick trial, is sentenced to life imprisonment in Deadman Wonderland, a massive theme-park-like prison. Arriving at the prison, Ganta is fitted with a special collar which tracks him and monitors his life signs. Due to the heinous nature of Ganta's 'crime', he is also sentenced to live out his imprisonment under Deadman Wonderland's 'Death Sentence'. A lethal poison is constantly seeped into his body through his collar, which can be kept at bay by consuming a peculiar candy-like medicine every three days. Additional candy can be earned through hard work or through purchase. In order to gather Cast Points, the prison's currency, an inmate has to perform in the facility's lethal games and survive to claim his prize. Fortunately for Ganta, he is aided by a mysterious girl named Shiro, who apparently knows Ganta, and by other prisoners as well, namely a kleptomaniac named Yoh. While trying to survive his daily ordeal as an inmate on death row, Ganta becomes increasingly obsessed with the 'Red Man' and tries to find him and clear his name. In an increasing bizarre twist, Ganta begins to develop a way to manipulate his own blood, to the point of turning it into a weapon. Unbeknownst to him, Ganta has become one of the prison's 'Deadmen', a segregated group of prisoners capable of controlling their blood. After his ability is discovered, Ganta is forced to participate into brutal gladiatorial death matches, known as Carnival Corpse, whose anonymous spectators pay large amounts of money to watch. In his struggle he manages to befriend some of those he fought off in the arena, and with them Ganta continues his quest to uncover the identity of the Red Man, why he turned into a Deadman, and the dark secrets the prison authorities are hiding.