A long time ago, the world suffered a great calamity and much of the land sank into the sea. While the beauty of the ocean remained the same, the creatures that inhabited it go through changes, and the people strongly rejected entering the sea.The people who lived on the little land that remained. One day, "it" appeared. A gigantic one with large wings emitting holy light on the world later called "Light of Judgement."The light gave power to people and life. It was the awakening and evolution of life. Not just people but also cats, dogs, pigs, and other animals.The world has changed. People joined hands with awakened animals and rowed out into the ocean once again. This is the beginning of the "Age of the Blue Sea."The Age of the Blue was also called the Age of the Blue Crystal. The Blue Crystal was the core of the Crystal Engine and a source of energy for all life. At the time, the people living on the land used the few blue crystals buried in the ground. On the other hand, people who set out to the sea discovered a large amount of Blue Crystal sleeping at the bottom of the sea.The massive discovery of Blue Crystals changed their life. The cities were constantly lit up, powered by countless spirit furnaces, and prosperity flourished. And so the Age of Blue Sea blossomed, and people began to set out to the sea in search of Blue Crystal.Meanwhile, guilds were created among those who were active in the ocean. Organized mining by the guilds led to a stable supply of Blue Crystals, and a stable civilization.The story begins in the midst of the flourishing civilization of the Age of the Blue Sea.