Deadman Wonderland 
Volumes 1 to 5 

-violence- gore - drama - action - killer/massacre - prison

"A powerful mysterious earthquake devastated the mainland part of Japan and largely destroyed Tokyo, causing three quarters of the city to be submerged in the ocean. Ten years later, in 2023, the story focuses on Ganta Igarashi, an apparently ordinary student attending high school in Nagano Prefecture. Although a survivor of the earthquake, Ganta has no memory of the tragedy and has lived an ordinary life. Everything changes when a strange man covered in blood and wearing purple armor floats in front of the classroom windows. Smiling like a madman, the Red Man massacres Ganta’s entire class and, instead of killing him, implants a red crystal shard into his chest. A few days after the massacre, Ganta is declared the sole suspect and, after a swift trial, is sentenced to life imprisonment in Deadman Wonderland, a prison combined with an amusement park built in 2017."