Made in Abyss (2017)

The Abyss. A chasm that never seems to end, stretching to the depths of the earth and filled with monsters. Despite the many adventurers who have ventured down and never returned, a girl named Riko wants to explore the farthest reaches of the Abyss. But as a novice, she is only allowed to explore the shallow parts. Nevertheless, she finds a robot that resembles a little boy named Reg. This leads her to believe that he comes from the deeper parts of the Abyss, and she decides to venture forth. The anime adapts the first three volumes of the manga in their entirety and ends with the first chapter of the fourth volume of the manga.