Made in Abyss (S1-S2)

An orphaned girl named Riko lives in the town of Orth on the edge of the Abyss—a colossal, mysterious pit plunging deep into the earth that contains remnants of a lost civilization and dangerous supernatural creatures. Riko dreams of becoming a legendary "White Whistle" explorer like her mother, Lyza, to explore its deepest depths. One day, while exploring the top layer, she discovers and activates a mysterious, highly advanced robot boy named Reg. Soon after, a balloon surfaces from the deep containing a message from Lyza stating she is waiting at the bottom. Determined to find her mother, Riko and Reg begin their hazardous, one-way descent into the terrifying secrets of the Abyss.