Kukangin (English: Voidsilver) is a special type of metal with spiritual suppressing properties, similar to Sekki-seki stone. It is primarily used by members of the Onmitsukido. It is rather costly to refine and scarce to find, so its usage is often rather limited.
Normally, Kukangin is a dark greyish metal with inky black veins running throughout it. The suppressing properties come into effect only when the metal comes in direct contact with being possessing spiritual energy.
A special version of neurotoxin-infused Kukangin exists in was very small quantities. The only visible difference between it and normal Kukangin is that veins are now a vivid amber color. While retaining the suppressant ability, any contact between a target's bloodstream and the metal will allow the toxins to take effect. The toxin is designed to impair brain activity such that the victim's ability to concentrate and react quickly is hindered. Removing the metal from the target's bloodstream removes the effect just as quickly as it set on, however.
The Augmented Kukangin was created by Sumiko Hadashi, at the request of and with resources provided by Kagechi Yorutora.