Extinct

AD 2047, the Earth was invaded by unknown extraterrestrial life form, named Ameba. Mankind was the major food of Ameba and 99％ of human were eliminated. Even the mankind tried to fight again Ameba, but facing the large scale invasion, they failed.

In order to preserve the human blood, the mankind built a bunker. They hide in deep underground to escape from Ameba massacre. They prepare to regain the Earth surface in some day.

As Ameba is an organic life form, they can penetrate the bunker a little by little through small slits. Even the bunker had strong and thick walls, they were not perfectly sealed. The bunker was finally fallen and the day was the dark day of mankind.

A girl awakens from slumber, she found herself in an underground facility. She lost her memory. Her name Nada is what she still remember. She is now trying to escape from this underground labyrinth.