Seven years ago, the world ended. An impenetrable fog rolled across the earth, swallowing everything in its path. No one who steps out into it ever returns. Hidden deep in a mountain valley in Japan, a small town survived. They built waterwheels, set up charging hubs and wind turbines, grew their own food, and adapted to a simple, self-sustaining life.

But behind their precarious and peaceful life, the ominous wall of fog continues to serve as a warning. Its secrets and mysteries forever haunt the fragile society, ready to plunge what remains of civilization into chaos.

Senior high schoolers Fukunaga Shouma, Araya Riyu, Takeishi Shishio, Yoshino Ume, and former police detective Kitou Honoka, with her informant Seino Yuuki, will soon be dragged into a danger that will decide the future of their last home. The enigma will soon unravel. And time shall continue its march, pulling their youthful days and this complacent lull toward the unexpected and the unknown.