The mysterious cave system Abyss is the last unexplored area in the world. Whole generations of brave adventurers, known as cave divers, have already devoted themselves to his exploration and many more will follow until all his mysteries are finally clarified. Since childhood, the young sage Riko has dreamed of becoming a legendary cave diver like her mother and following her into the depths of the Abyss. On an exploration tour of the higher levels of the Abyss, she makes a discovery that will turn her whole life upside down... A gloomy fantasy epic that is second to none.