Green, lush, and calm Ooshima island floats in the Seto Inland Sea. Once a peaceful place, now a land full of desire and insanity. UNKNOWN - LEVEL 4, the infectious disaster that they should have escaped, recurred in this place. Many infected people wander the city, and violent acts by them are spread everywhere. In trying to escape from this confusion, Makoto, Ayatsuki, Ayanagi, and Taya were leaving town through the woods. They were proceeding blindly but decided to aim for the shrine where Rey Murakami is, a close friend of Taya. The infection spread more quickly than expected, and infected people were already wandering the forest...