Ō Sen holds the rank of Great General in Qin's military and leads the influential Ou family, cousin to the late Great General Ou Ki. A man in his fifties with a tall, warrior's build, he presents an imposing figure. His face remains largely hidden behind distinctive Asura-inspired helmet and armor, revealing only a strong jawline, black mustache, long goatee, red eyes, and pale brown skin. He harbors a deep-seated ambition to build his own kingdom, a goal recognized by figures like Shou Bun Kun and noted as the reason King Sho never favored him, despite his military prowess. This ambition drives his strategic choices, such as recruiting defeated commanders like Kyou En with promises of land in his future realm. He openly declared this aspiration to Ri Boku, criticizing hereditary rule as a fatal weakness. Ō Sen's personality is marked by extreme stoicism and emotional detachment. He speaks sparingly, rarely raises his voice, and offers no explanations for his orders. His approach is one of calculated caution, engaging only in battles he believes winnable and prioritizing survival over unnecessary risk. Despite this reserve, he demonstrates subtle benevolence, forbidding harm to civilians during the Gyou Campaign and sparing enemy commanders for potential recruitment. His relationship with his son, Ou Hon, is distant and strained, fueled partly by rumors questioning Ou Hon's paternity. Nevertheless, he intervened to correct Ou Hon's spear technique in childhood and later chastised him for reckless decisions in battle. Renowned for meticulous preparation and psychological warfare, Ō Sen lured Kyou En into a trap during the Sanyou Campaign and built a hidden soil fortress to counter Ren Pa. He defended Qin's mountain passes against Yan's Ordo in the Coalition Invasion using attrition and strategic retreats. During the Gyou Campaign, he enforced strict discipline against pillaging and utilized unexpected allies like the Hi Shin Unit. He often attributes victories to his subordinates' combat prowess rather than his own strategies. His history includes service under Great General Mou Gou and membership in the Six Great Generals before stepping down after defeat at the Battle of Hango. He later reclaimed the title of Great General after the Gyou Campaign. Key figures include A Kou, a former enemy recruited by his kingdom-building ambition, and Kan Jou, an officer assigned to oversee Ou Hon's development within the Gyoku Hou Unit.