Sleepy eyes of death 8: sword of villainy (1966)

Nemuri Kyoshiro discovers a conspiracy centering around a band of disgruntled samurai wanting to avenge the death of their sensei, a political reformer that pushed for better provisions for the lower classes until he was assassinated by Shogunate agents. Their plot, to set fire to the oil refineries of two rich merchants and unleash a raging inferno that will hopefully burn down the Edo Castle.