Made in Abyss
The Abyss is a deep and mysterious chasm that stretches deep into the earth. Legends tell of its many creatures and relics from a distant past, and many explorers, known as Divers, have set out to explore its depths and uncover its secrets. The most experienced of these Divers are known as White Whistles, and they are revered as heroes.
Riko, the daughter of a legendary White Whistle named Lyza the Annihilator, dreams of one day venturing into the Abyss and following in her mother's footsteps. Unfortunately, as a novice Red Whistle, she is only allowed to explore the uppermost layers.
One day, she meets a mysterious robot boy with no memory of his past. Intrigued, Riko names him Reg and they decide to go on an adventure to the bottom of the Abyss to uncover his memories and discover its secrets. But they soon realize that the Abyss is a much more dangerous place than they had imagined.