The enigmatic Abyss entices those with the spirit of exploration, despite the dangers. Wishing to follow in her mother's footsteps, Riko trains hard to become a Cave Raider. One day, she receives news that her mother died in the Abyss, yet a mysterious note tells Riko that her mother may still be alive. Vowing to uncover the truth about her mother's fate, Riko embarks on a journey with a humanoid robot boy name Reg. Together, they will discover if they have what it takes to survive where so many others have perished. Source: sentai filmworks Note: Two compendium films drawn from the TV series together with newly added scenes and storytelling.