Tokyo, 2022. Skies crowded with drones have become an everyday sight. One day, Yui Yazaki (Mori), a chief appraiser at a real estate company, visits a newly purchased condo with her subordinate Kobayashi. Just as they finish the inspection and prepare to return to the office, a blinding white light engulfs them. After a drone believed to be carrying a biological weapon crashes, they are forced to take refuge in a shelter on basement level three until decontamination is complete. Just the two of them, sealed away together. And then...