The Abyss, a curious place shrouded in mystery. A wide-open chasm, the only place on Earth that remains unexplored. A place that is both captivating and menacing. Rico, a young orphan girl, spent her childhood in a small town perched atop this chasm, dreaming of becoming an explorer, just like her mother. One day, as she descends into the chasm to explore it as a speleologist, she stumbles upon a strange robot that bears a striking resemblance to a human being. Together with this robot, she will attempt to uncover the secrets of the Abyss...