The narrative unfolds in an unnamed timeline where humanity possesses highly advanced technology. Nevertheless, the human population is declining, and it appears they are heading toward extinction. The protagonists are Leos Alloy, Sthesia Awar, and their Haro. They operate on a Jupiter base known as "Jupiter X," utilizing "General Answer" (or "GA"), which houses a vast repository of data regarding the alternate history of Humanity. Leos travels to the Earths of these alternate timelines in an effort to gather data that might provide a clue regarding the evolution of mankind.