Made in Abyss

Twelve-year-old orphan Riko lives in Orth, the town perched over the Abyss, a vast pit that plunges into the earth and gives up relics to the Cave Raiders who descend it. She dreams of following her mother Lyza, a legendary White Whistle who vanished below. When she discovers Reg, a boy with a robotic body and no memory, in the upper layers, the two resolve to descend together toward the bottom, knowing the Abyss inflicts a worsening curse on anyone who tries to climb back up.