Yukimaru Sanada leads the Seven Samurai, a group sworn to protect Fena Houtman. His connection to Fena began in childhood when he saved her during a violent ship attack on her family. After ensuring her escape on a lifeboat, Yukimaru suffered severe injuries. He was rescued and rigorously trained by Kei, becoming an elite warrior under Sanada Yukihisa's command on Goblin Island. His lineage ties directly to the historical Sanada clan, reflected in his name and personal emblem.

Physically, Yukimaru is tall with black eyes and long black hair, typically secured in a ponytail by a grey ribbon. As a child, he had grey-brown eyes and shaggy brown hair. His early attire consisted of a black haori, a red scarf, and dark grey pants, often going barefoot like his comrades. His combat outfit evolved into black armor featuring sode shoulder guards and kote arm guards, complemented by red leg guards and black boots. This was later updated to include red arming garments and a grey undershirt. His signature red helmet bears antlers, the Sanada clan emblem, and facial armor. He wields two samurai swords.

Personality-wise, Yukimaru is introverted and stoic, prioritizing duty above all else and demonstrating strong leadership within the Seven Samurai. His protective instincts toward Fena, rooted in their shared past, dominate his actions. He struggles to express emotions openly, often reacting with visible ear-flushing when embarrassed or teased about his feelings for Fena. Despite his reserved nature, he exhibits unwavering loyalty and a readiness to sacrifice his life for her safety.

In combat, Yukimaru emphasizes exceptional swordsmanship and agility. He delivers rapid, precise sword strikes capable of efficiently dispatching multiple opponents, utilizing techniques like a flash step for swift movement. These skills establish him as the most formidable swordsman in the group.

Key relationships define him. His bond with Fena intertwines childhood history, protective duty, and unspoken romantic tension. He frequently clashes with her over safety concerns but remains deeply devoted, culminating in a direct love confession. Among the Seven Samurai, he commands respect as their leader, though his aloofness occasionally strains interactions. Shitan frequently teases him, and their dynamic carries underlying tensions related to mission objectives. A significant rivalry exists with Abel Bluefield, the murderer of Fena's father, fueling Yukimaru's resolve for vengeance.

Yukimaru's journey centers on reconciling duty with personal loyalty. Initially focused on escorting Fena to Eden under Sanada Yukihisa's orders, he later defies commands to abandon her, choosing instead to protect her unconditionally. This marks a shift from obligation to personal commitment. Critical moments include sustaining multiple injuries while shielding Fena from threats like Maxiver Jr. and Abel, and confronting Shitan over perceived betrayal after learning the mission's true intent. His climactic battle against Abel results in severe, near-fatal wounds, resolved only after Helena's spirit intervenes. Following Fena's transformation and memory loss at Eden, his vow to restore her memories and final confession trigger her partial recollection, reinforcing his role as her emotional anchor.