An orphaned girl named Riko, who finds and befriends a part-robot boy named Reg, and descends with him into the titular "Abyss" that leads deep into the Earth, in hopes of exploring it and finding her mother, along with Nanachi, Faputa and the Autobots. Who ended up in the abyss in some mysterious way.

Riko, Reg, Nanachi, Faputa and the rest are right now in the second layer of the Abyss. Which is a bit more intense. Since the Curse takes form of causing Vertigo, Dizziness and Nausea.