The introduction of firearms to Japanese military tactics quickly rendered the Samurai antiquated, and the Satsuma Rebellion resulted in the government outright banning many aspects of their life. Scores of them chose to take their own lives rather than suffer the shame of this, while some became teachers of the police forces. Others started down the road that eventually led to the Immortals. A few hid themselves in secluded areas of the mountains, continuing to practice the old ways.
For years, they were ignored; especially after the outbreak of the great war. Their seclusion kept them ignorant of the worldwide conflict but, about a year ago, three men arrived in Shanghai dressed in the traditional naga-bakama and seeking audience with the new Emperor. They offered the services of their most elite warriors in exchange for acceptance within the Shogun Empire. The Emperor was skeptical of their use after the Rebellion, so he demanded a demonstration, to weight the validity of their claims.
In a large courtyard, the three Samurai were pitted against the three squads of Manchurian Infantry. In a display of speed and skill that left everyone in awe, the warriors flashed across the courtyard and cut down two of the squads before the rifleman could draw a bead, then eliminated the third with firebombs hidden within their clothing. Impressed, the Emperor agreed and gave the Tsuwamono a place within his army.
This unit is immune to fire damage. That makes it tremendously useful for rushing through the effects of attacks from units such as the Korean Archers.