27-year-old Hotta Youta was a virgin, a high-school dropout and a former hikikomori working in a metalworking factory. His life has been a living hell from childhood on, and on his way home from work one night, he is stabbed to death by a drug addict. Youta is reborn in a fantasy world as a baby named Lute, but with the memories of his life in modern Japan. Upon learning about a rare magic tool called "Magic Liquid Metal", he puts his knowledge of guns and metalworking to work in creating guns for himself and his childhood friend Snow in order to survive in this new world.