In some near future, a biological agent released by terrorists has brought humanity on the verge of annihilation.
The disease has the particularity of having prominently acute effects on adult beings, causing the life expectancy to drop greatly.
The story begins with two youth groups arriving at a deserted school. The two communities are suspicious of each other, but somehow manage to cooperate and live alongside. Close by is a shopping mall, and they think of settling down for a while. Yet, on their first day at that place, a radio broadcast from the Shinjuku Tokyo Metropolitan Government prompts whatever human being still alive to join them.
This announcement stirs conflicting discussions on whether to go, since the place is nearby, at most two or three days away. They fail to reach an agreement, the opponents being reluctant to take unnecessary risks now that they've found a relatively safe haven.
The day after, several members leave. No one knows what happened to them thereafter.