In this well-explored world, the last secret area, a huge pit of fathomless depths, is known as the Abyss. Nobody knows where this huge vertical cave finally leads to. Inside there are various rare creatures and treasurable relics beyond the modern manufacturing facility. The amazing Abyss entices those with the spirit of exploration to descend into it one after another. An orphaned girl named Riko lives in the Belchero Orphanage in the town of Orth, The City of the Great Pit around the edges of the Abyss. She dreams of following in her mother's footsteps, who is "the Annihilator," a legendary White Whistle, to uncover the mysteries of the Abyss.One day, while exploring in the Abyss, Riko meets a humanoid robot...
