Replying...
Intro. It all starts with Yuri Honjo, a normal high school girl, who suddenly wakes up on top of a giant skyscraper, in a strange world of sky-tall buildings connected by rope bridges — no floor, no way out. She calls her brother Rika for help, but soon sees a guy with a smiling white mask (a "Smiling Mask" ) killing someone with an axe. Panic begins While fleeing, Yuri encounters a masked police officer (another Smiling Mask disguised as a police officer). He shoots the masked man who was chasing her, seeming to save the girl... But then the terror turns: the policeman kills his own companion (another policeman) mercilessly, just to be alone with her. He starts threatening Yuri, forcing her to take off her clothes slowly, saying disgusting things like "take off everything but her socks" — humiliating her to force despair and suicide (because the masks want to see people reach the limit of desperation to kill themselves, otherwise they kill themselves).

Yume, the Silent Marksman

@Miguel