Noro (ノロ, lit., "slag") are impurities removed from iron sand during the process of purifying Tamahagane. As this substance also contains traces of divinity, they are almost indestructible and is instead handled with extreme care. Noro has a special property of easily binding together with itself, which if left unchecked, results in the creation of Aradama, creatures that bring forth calamities into the world. In order to prevent this transformation into Aradama, a long-standing tradition of dividing Noro into pieces, sending the pieces to forests as offerings, and suppressing them is performed.
Despite the regulation in Noro, the Origami Family stockpiles large amounts of Noro deep within the family's main shrine. Noro is also administered in injection pens.Noro is the source of new technology like Spectrum Finder and S-Equipment. Injecting Noro into human will increases the injected human power, turning user into artificial/half aradama. But because this technology is still unstable, the body can't withstand if too much Noro is injected, resulting in the user losing sanity, damaging body or even mutating into full Aradama.
It is revealed that originally Noro that form Aradama will be destroy by Toji, the remain Noro afterwards is enshrine by the Toji who also is shrine maiden. After the Meiji Era, the number of shrine being reduced because of the economic problem, the action resulting the amount of enshrined Noro being reduced, and potentially create more Aradama. To solve the problem, Origami Family and the Government decide to gather Noro for easier management. Because of the threat from the incoming War(possibly the World War), Noro demand for military research increases, in order to apply the divine power for military use, the power which normally only Toji can use, so the regulation in Noro being removed. After the War, Noro gathering increase with the involvement of U.S military for researching purpose with the excuse of gathering Noro for easier management, they start gathering Noro accross Japan. But according to Richard Friedman, the more amount of Noro gathering in one place, the more intelligent it will become, and it will cause disaster. The Great Disaster of Sagami Bay is the result of trying to gathering Noro in one place.