After the events of Made in Abyss: Dawn of the Deep Soul, Riko, Reg, and Nanachi enter the weird bubble ship and descend through a deep ocean into a sunny land--the titular "land of the scorching sun.

The story follows an orphaned young girl, Riko, who finds and befriends a humanoid robot Reg and descends with it into the titular "Abyss", that leads deep into the Earth, in hopes of finding her ...