"Armored Trooper Votoms: Red Shoulder Document - Roots of Treachery" is a four-episode OVA series that serves as a prequel to the original "Armored Trooper Votoms" anime. The story is set during the Hundred Years' War between the Balarant Union and the Gilgamesh Confederation, focusing on the elite Red Shoulder Battalion, a notorious unit known for its ruthless tactics and unparalleled skill in piloting Armored Troopers (ATs). The narrative centers on Yoran Pailsen, the commander of the Red Shoulders, and Chirico Cuvie, a young soldier who later becomes the protagonist of the main series.

The OVA begins with Chirico being transferred to the Red Shoulder Battalion after displaying exceptional combat abilities. Under Pailsen's command, the Red Shoulders are tasked with executing high-risk missions that often involve morally ambiguous objectives. Chirico quickly becomes disillusioned with the unit's brutal methods, particularly when they are ordered to massacre civilians suspected of harboring enemy sympathies. This internal conflict is exacerbated by Pailsen's increasingly erratic behavior and his obsession with creating the perfect soldier, which leads to unethical experiments on his own troops.

As the story progresses, Chirico uncovers the darker aspects of the Red Shoulder Battalion's operations, including Pailsen's secret project to develop a super-soldier through genetic manipulation and psychological conditioning. The tension between Chirico and Pailsen escalates, culminating in a confrontation where Chirico questions the morality of their actions and the true cost of their victories. The OVA concludes with Chirico's eventual desertion from the Red Shoulders, setting the stage for his journey in the main series.

The narrative explores themes of loyalty, betrayal, and the dehumanizing effects of war, with a particular focus on the psychological toll it takes on soldiers. Chirico's struggle to maintain his humanity in the face of overwhelming brutality serves as a central thread throughout the series. Pailsen, on the other hand, is portrayed as a complex antagonist whose descent into madness reflects the corrupting influence of power and ambition. The OVA provides crucial backstory for Chirico's character and offers insight into the origins of the Red Shoulder Battalion, enriching the broader "Votoms" universe.