Immoral Quartet is an erotic Visual Novel.

One day, humankind suddenly went to extinction.

For no apparent reason, a large number of people die every day, and their daily lives disappear.

A month after the event, only four men and women survived on an offshore island 200 kilometers south of the capital.

Still students, they gather in the school building and work together to live.

During the day, he works to gather information and secure food, and at night, four people eat together.

It was natural that a special feeling for the opposite sex would sprout in such a life of sleeping and eating together.

However, the excess libido gradually upset the relationship between the four.

The apocalyptic world reveals their true nature ....