Sōichirō Nagumo, a middle-aged man whose strong, muscular build commands attention, rarely steps out without his signature gray long coat—a garment reflecting his no-nonsense demeanor. Prior to adopting the title of Horse Knight, he served as a police detective, a career that forged his disciplined approach to leadership and unshakable sense of duty. Now leading the Beast Knights, he operates as both strategist and shield, guiding younger teammates with a vigilance honed by years of protecting others.

Nagumo defines himself through steadfast leadership, unwavering protective instincts, and a tactical mind that leaves little room for frivolity. In combat, he commands formidable skill, most notably his "hundred kick" technique—a devastating barrage of precision strikes designed to dismantle adversaries swiftly. His peers rely on his calculated decisions and proven expertise, solidifying his role as the group’s anchor in turbulent times.