Tenkuu Shinpan

High-school girl Yuri suddenly finds herself on the rooftop of a high-rise building. Shes trapped in a bizarre world surrounded by skyscrapers, where a masked man cracked open a mans 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.