Immoral Quartet ~4-nin no Seiyoku ga Karamiau, Ai to Netorare no Monogatari~

Humanity has gone nearly extinct. A vast number of people have died for no explainable reason. The everyday lives of all humans everywhere have been utterly shattered. Just one month after this horrible tragedy, there are only four sole survivors on a floating island south of the capital—two men and two women. They must work together to survive, gathering information and securing food in the morning and eating together at night. However, as time passes, tensions begin to arise as the reality of their situation sinks in. Can the four of them work through these difficulties to survive the apocalypse?