what we know for sure is that it 100% is not just basic armament haki or ryou. even fucking bums like kinemon, kiku, and kawamatsu and even hyogoro can use ryou. when the scabbards cut kaido, the cut wasn't permanent at all. kaido sensed oden's haki at that point as well. im 99% sure that it's either some weird way of imbuing CoC in your blade or asura.