The protagonist was originally a killer affiliated with the organization. He was later released by the organization and regained his life, but he wasted his life and finally died due to an accident. Fortunately, the organization's superiors transferred the protagonist's consciousness to a new body, and he will live again as a 17-year-old high school student.
Concept: Law of the Flood: What does not belong to this era will eventually be lost, and the flood has its own direction.