Most events in Kansen 4 take place “The Day After” the endings of Kansen 1 and 2, during the reclamation of the contaminated areas by the Japan Self-Defence Forces.
Daisuke Sendou just enjoys his school life with his classmates. One day, they go camping just before summer holiday (therefore escaping the initial outbreak of the Unknown virus epidemic), but… A cruel result is awaiting them there…