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.

with the full name Made in Abyss: The Golden City of the Scorching Sun. Anime-on-Line describes it as follows: "No one has ventured into the sixth layer of the Abyss and remained unchanged.