There is no going back for Riko, Reg, and Nanachi. They have passed the point of no return and the surface is forever out of reach. Now, Riko's only way forward is to the bottom of the Abyss. However, the three friends weren't the first to enter the unknown; they were only the most recent. Whatever happened to all the other explorers who braved the deepest layers of the Abyss and were never heard from again? The trio are about to find out.

[Source: Sentai]