This is a place 6,000 meters deep under the Atlantic Ocean. It is a world belonging to undersea humans. It was once the territory of the most glorious deep-sea country-"Onishi Country".
100 Years ago, an abyssal catastrophe destroyed the once splendid underwater civilization and extinguished the light of the ocean, the energy source on which deep-sea humans relied for survival. The deep-sea world has since entered the "Dark Age." Prince Randy of the Great Western Kingdom was frozen in a purple-gold iceberg and sent to the Antarctic, where he was sleeping and waiting for the call of the light of the ocean to revive.
100 Years later, when the prince woke up, his memory had disappeared. He had forgotten his identity, his mission, and the most important person in his life a hundred years ago. He was on a sunny Greek island, living in a daze. It wasn't until he met the girl of his destiny that his memories began to jump. Then the magical characters from the deep sea appeared one after another, and an adventure was about to begin. And the tall black figure in his memory, the cold killer who walked out of the dark abyss, the figure inseparable from his destiny will also return. This begins a new chapter in Onishi Kingdom. . . . . .