Ren Chitose, also called "Zero", is a 15 year old bullied child who sees no hope in the future. However, one day, his life is turned around when meeting Ena, "One", a Goddess who has fallen from the Heavens during a nearly never-ending war that has been going on for hundreds of years, unapparent to humankind. According to Ena, gods and goddesses need vessels to become a weapon of to maximize their power in the war, and humankind is meant to be their vessels. Ren accepts Ena's offer for him to become a vessel as they go to the Heavens, as there was never a place for the both of them in the earths.