In the underwater world of Rhoton, Sirens live on the raging battleground, hoping to reclaim their lands from the Demons one day with the help of the various animal species. Allen is youth born to this life, in the city of Pearl, and his greatest dream is to explore the corners of the ocean and someday, find earth. He and his companions will experience all the challenges the ocean has to offer, and he will rise to be something even more than an adventurer.