Also known as: リビルドワールド
A web novel by Nahuse, that got officially published as a light novel with illustrations by Gin, environmental design by yish and mechanical design by cell. It also received a manga adaptation by Ayamura Kirihito. An anime adaptation was also announced.
It tells the story of Akira, a dog-eat-dog New World orphan living in the slums. The Old World civilization had extremely advanced technology to the point of nigh-omnipotence, but destroyed themselves in wars, resulting in the rise of the less modern (but still significantly advanced) New World. Despite the extinction of their masters, Old World AIs still have control over the ruined infrastructures, endlessly manufacturing monsters to destroy the New World and reclaim it for them. As Akira can receive signals from the Old World, one day a mysterious AI makes contact with him and offers to help him in exchange for his assistance in exploring a certain ruin.