Benimaru began as the unnamed prince and heir apparent of the ogre tribe's chieftain, destined to lead. His tribe faced annihilation by the Orc Lord's army, forcing him to flee into Jura Forest with his younger sister Shuna and five survivors. Mistakenly attacking Rimuru Tempest, believing him responsible, they soon realized their error. After apologizing, they formed a temporary alliance with Rimuru, which solidified into permanent loyalty following the Orc Lord's defeat. Rimuru then bestowed the name "Benimaru," triggering his evolution from ogre into a kijin, a rare human-like form, marking the start of his service as a key subordinate. Physically, Benimaru transformed significantly. As an ogre, he possessed red skin, long crimson hair, dark horns, sharp eyes, and a tall, muscular frame, clad in samurai-style armor influenced centuries prior. Evolving into a kijin reduced his height to roughly 180 cm, gave him human-like skin and sharpened features for a younger look, leading to simpler attire and later a signature red, yellow, and white kimono. Distinctive red vertical facial marks are childhood scars from an accident involving Shuna. Subsequent evolutions, fueled by Rimuru's ascension to Demon Lord, transformed him first into an Enrei-Oni (Flame Spirit Ogre) and then a Flame Demon God, amplifying his imposing presence. Benimaru's personality blended carefree confidence, battle-love, underlying caution, and strategic cunning. Initially hot-headed, his role as Rimuru's military commander fostered greater rationality and calm. He values strength and loyalty but disdains leading the unworthy, though avoids belittling the weak. A deep sense of duty to Rimuru and his people contrasts with personal hesitations, particularly regarding romance—he remains awkward around interested women. Despite his warrior persona, he harbors mundane preferences, loving sweets and disliking carrots. He eventually married Momiji, a tengu, and Albis, a beastkin, having children with them. Within the Jura Tempest Federation, Benimaru holds critical positions: Minister of Defense, Commander-in-Chief of the military, leader of the Fourth Army, and a prominent member of the Twelve Guardian Lords. He ranks among Rimuru's top three strongest subordinates alongside Diablo and Zegion. His tactical mastery earned him the moniker "Flare Lord," reflecting his skill in battlefield strategy and troop coordination. His combat prowess centers on swordsmanship and fire manipulation. Trained by Hakurou, he wields the mythical katana "Guren" (Crimson Lotus). Fire skills include the regeneration-negating Dark Flame and the incinerating dome of Hell Flare. His Unique Skill "Born Leader" (formerly "Grand Marshal") enables precise power control and battlefield prediction via energy flow analysis. This evolved into the Ultimate Skill "Lord of Sunlight" (Amaterasu), granting dominion over fire and light, spatial and temporal manipulation, thought acceleration, and absolute sensory perception. Defensively, he employs Multilayer Barrier for near-permanent protection and resists physical, elemental, holy, and mental attacks. Post-evolution, his power reached continent-level threat status, capable of challenging Awakened Demon Lord-level opponents. Benimaru shares profound mutual trust and loyalty with Rimuru, whom he addresses as "Sir Rimuru." He defers to Rimuru's authority while occasionally joining his unconventional plans. His bond with Shuna is protective and trusting; he relies on her for domestic management. Among his fellow ogre survivors—Shion, Souei, Hakurou, and Kurobee (who forged his katana)—he maintains camaraderie. A rivalry exists with Diablo over being Rimuru's strongest subordinate, though Benimaru acknowledges Diablo's capabilities. Externally, he interacts with figures like Milim Nava, sharing an aversion to vegetables. Key events include decisively wounding Charybdis while leading Tempest's forces and participating in major conflicts like the Empire Invasion Arc. His growth is marked by creating techniques such as "Oboro Black Flame: Hundred Flowers" and "Prominence Acceleration," plus collaborative attacks like "Quartet Skill: Breakdown Nostalgia." Beyond combat, he contributes through fire prevention initiatives and snow-clearing duties.