Azure oil is an alternative to crude oil found in the deep caverns of Tatsu, Tekkan, and is known for its technological breakthroughs, delivering the Tatsu Clan dominion, and a turning point in Tekkanese culture. Discovered by the mineralogist, Kotaro Shima in 2927 RH, who was originally looking for coal to smelt and fold his metal came across what seemed to be an iron deposit painted blue. After months of research, Kotaro found that the iron could be cracked open and spill a liquid that behaved similarly to crude oil—naming it azure oil for its blueish tint. The oil, while being capable of uses similar to regular oil, was able to do much more. Like conducting electricity, tinkering with biomatter, and amplifying sulfur products and explosives. The metal shell scraps that the oil came from could also be used as a premium refined metal known as ao hagane.

Azure oil and Ao hagane today are expensive yet valuable materials that are used in assembling most of the arsenal of the Tatsu Shogunate which gave them an upper hand during their battles in Yamamura and Azuhanto.