In front of sixteen-year-old Yuri Honjo, a stranger's head was cut open with an ax. Horrified, Yuuri realizes that now it is her turn and the strange masked assassin is heading towards her. Yuuri, who was in her home school a second ago, cannot even imagine where she ended up and how. One thing is clear - you need to be saved. Running out the nearest door, Yuri sees that he is in a high-rise building, where there are no people, and the doors leading to the lower floor are locked. Seeking help, Yuuri, pursued by a maniac with an ax, ends up on the roof. Before her opens a view of a completely unfamiliar city, where there are other high-rise buildings, the roofs of which are connected by suspension bridges, and other maniacs in masks. A weak girl without weapons and superpowers, Yuri can only rely on his own ingenuity and desire to survive. Well, and perhaps for luck, which, as you know, is also far from an unimportant factor. Upon learning that her brother Rika has also ended up in this dangerous world, Yuuri gathers up the courage to fight for survival and decides to find him so that together get out of this monstrous place.