Sakugan!!

The distant future, long after the Western calendar is no longer used. Humans live shoulder-to-shoulder, cramped in the "Labyrinth," an underground world deep below the surface. There are many colonies where people live in the underground Labyrinth. The place is known for extreme high temperatures, but also for lodes of gold, silver, and other riches. In one of the colonies named Pin-in, a curious nine-year-old girl named Memenpuu and her father Gaganbaa board a two-person work robot and mine for ore. They eke a living as the lowest of lowest "Worker" occupations.

One day, Memenpuu begs her father Gaganbaa to set out as Markers — those who chart the innards of the Labyrinth as a spelunker — to search for her mot...