Void: No. Nine - 9-banme no Utsuro

"We are the ones who run to the end of the line."

A post-apocalyptic limited-time job. It's been 300 years since the world was destroyed. The job is to recover relics.

In a disposal tunnel 50 meters below the Reclamation City No. 9, nine people with histories are gathered by a certain organization. Divided into groups of three, they collect “relics,” “minerals,” and “gold items” to receive rewards. Will they be able to survive as they encounter traitors and emissaries from the old world lurking in the underground tunnels, all with different backgrounds and lifestyles? A near-future, underground incognito mystery.

(Source: Kadokawa, translated)