High-school girl Yuri suddenly finds herself on the rooftop of a high-rise building. She’s trapped in a bizarre world surrounded by skyscrapers, where a masked man cracked open a man’s head with an axe before her eyes. Finding a way to survive this bizarre world, find her beloved brother, and escape becomes her top priority, but she is beset by danger not just from the mysterious Masks, which possess both inhuman strength and cruelty, but other survivors turned cruel or desparate by the insanity of the high-rise world.Upon witnessing a man’s head cracked open with an axe, 16-year-old Yuri Honjou trembles in fear and confusion as she flees from the masked assailant, only to find out she’s trapped in an abandoned building where every door is mysteriously locked. Desperately searching for a way out, Yuri runs to the rooftop, but a world with no signs of life stands before her, surrounded by high-rise buildings. Though filled with despair, once she learns that her brother is also in this strange place, Yuri is determined to find him and escape. However, she soon finds that there are more masked murderers in the area, anxious to terrorize their newfound victims and satiate their sickest desires, leaving Yuri to question if they will be able to make it out alive.