Fourteen years ago, an environmental disaster known as the "Hammer of Eden"” devastated the planet – taking with it six billion lives, and submerging 90% of the world underwater. In the present, the remaining countries have formed a new United Nations in hopes of peace. Gould, a submarine captain, wishes to use military force to obtain this goal, while Aoi, the secretary general of the UN, believes in the power of diplomacy. In this world, Keel and Teen are twin siblings who, through a series of events, travel separately with Gould and Aoi. Together, they seek to answer the same question: is war the only way to attain peace, or can people learn to set aside their differences and negotiate?