During the summer vacation of 1988, second-year junior high school students Shun Kurata and his friends set out on a treasure hunt trip from Tokyo to Nagano Prefecture . However, in the midst of this, a nuclear war breaks out, and Jin, who was exploring the cave, is buried alive. After digging out a stone and escaping on their own, they find a war-torn world 13 years later. In order to protect themselves, Xun and the others pick up weapons and start walking toward their hometown of Tokyo, amidst an army of nobility.