Kyoukai Senjou no Horizon chronicles the story of a futuristic civilization returned to Earth after constant warfare hindered the beyond the post-Apocalyptic Earth At this stage, a so called the Divine States were the only hospitable land on Earth In order to regain the space-faring technology they had lost after many years of war, they decided to recreate history with a book called the TestauideIt is the year 1648 in the Testament Era Toori Aoi, Chancellor and Student Council President of the only academy on the airborne city-shi p Musashi , faces the ten-year anniversary of the death of his childhood friend Horizon Ariadust in an accident As he prepares to celebrate the occasion by proposing to P-01s (an automaton who looks exactly like Horizon) he discovers that his suspicion about P-01s’ appearance actually has a basis in truth; P-01s is in fact Horizon Ariadust, reborn into a robotic body In addition to this, Horizon’s eht powerful weapons called the Mortal Sin Armaments; which are now in the possession of key people in various established countries in the Divine StatesTo retrieve the e with his friends and allies begins a crusade against different obstacles as key events in history are recreated in a futuristic manner