It was night and Atsushi had an unsettling dream of his past in the orphanage, where an out-of-place door painted with a white tiger is engulfed in fog. He got woken up by his roommate Kyōka, who also dreamed of the fog. The two soon realised that Yokohama has been engulfed in the mysterious fog, and everyone but the various ability-users have disappeared from the city...