Fukumen no Hitsuji

Overview

People with crazy worries visit the basement. A masked "guide" awaits such lost visitors. The "guide" says, "Never tell anyone what you see or hear here." At a facility in the basement of a hospital, human clones were secretly made at the request of customers. Anyone who breaks the secrets of the clone or breaks the rules will be dealt with promptly by the execution team.

Source: AniList