Time passes slowly on the earth, and human beings continue to develop and grow. Finally, the appearance of mysterious resources and organizations one day breaks the balance of the world. The end of the world is coming, they say, and they begin to devour life, leaving the earth riddled with holes. Even if the sky is covered with ashes, there is no light all day long, and the plague is rampant at the end of the world, people have not given up on the beauty in their hearts. As time went by, people regained large tracts of land and created beautiful city fortresses in a harsh environment. A young boy wakes up in an underground laboratory abandoned by a mysterious organization. He has no memory and thinks he is a surviving experimental subject. By chance, he met a black-haired man who seemed to know him underground. He was picked up and brought back to the human city fortress, where he began to live in a hug. As the boy's understanding of the world increases and his strength recovers, his memories begin to piece together slowly, and the truth about the apocalypse and the organization's conspiracy slowly emerge.