Humanity has been waging war for the past 400 years in what has been known as the Extinction War. The world has effectively been destroyed during the war, rendering earth unsuitable for life. The remaining countries are forced to live in glass domes where they continue to wage war on each other. Some people are unable to live in these domes due to limited resources and are forced out to try and survive by themselves. Suzuki Sora is one of these survivors and is hiding out with a group of other survivors in an underground hideout when one day the hideout is caught in the middle of a conflict between two countries and the majority of the group is killed by a nuke. Sora regains consciousness in an underground stronghold in another world. Unable to leave the stronghold, he finds the crystal of knowledge which offers him a way to leave the stronghold in exchange for taking the crystal along with him when he leaves. Sora accepts the offer and is given abilities to assist him. Now armed with new abilities, Sora makes his way into this new world with hopes of using this second chance to experience the world that he was unable to. However, with the crystal of knowledge missing from the stronghold, foreign powers take advantage of this fact.