Kurai Jigoku was often thought of as a misfit, as he was frequently picked on by those in his school. He was not particularly rich and had to purchase inexpensive shoes, and sometimes had to repeat the same outfit every day. Kurai endured numerous forms of torment from his classmate Sado Yorimitsu, such as stealing his money, giving him physical abuse that left his bones broken and his face disfigured, and even forcing his head into a toilet. He experienced every type of bullying imaginable. The unsympathetic and callous teachers and students ignored Sado's clear mistreatment and regularly put the blame on Kurai for initiating conflicts, although this was not accurate. Kurai caused his mother to be ashamed of him, leading him to sink into depression. He made attempts to end his own life, but ultimately lacked the resolve to go through with it. "I'm simply gonna die a loser because that's what the world wants? It's not fair, I can't stand it." "Good, hero? Screw that. There is no such thing as hero in this world." Kurai yearned for the opportunity to take revenge on everyone who had made his life miserable. One day, following Kurai's altercation with Sado, his dream came true as he and his peers were summoned by a Goddess to an alternate world. He was no longer the same as before; he could now life forever and is ageless, even if he was broken down to the last atom, he would be able to come back together again. He vowed to have his opportunity to exact retribution on Sado, who holds the title of hero, and to take him out by any means necessary.