Tengai no Vault summary: A world where mysterious objects known as \"Artifacts\"—capable of triggering phenomena that defy human understanding—have appeared. Humanity lives divided between two realms: the \"Upper World,\" where a colossal city has been built, and the \"Lower World,\" a vast and ruined wasteland. While carrying out a solo mission in the Lower World, Tezuka, a member of a special task force that collects these Artifacts, searches for clues to find his missing sister...