Rimuru Tempest began existence as Satoru Mikami, a 37-year-old Japanese salaryman killed while protecting colleagues from a stabbing. At death, an unknown voice granted abilities for his next life, resulting in reincarnation as a small, blue, translucent slime roughly 40 cm in diameter within a fantasy world. Lacking conventional senses initially, the slime later acquired skills such as Magic Sense. Early actions included forming a pact with the sealed Storm Dragon Veldora, who named him "Rimuru Tempest" in exchange for a promise to break the seal. Rimuru consumed both Veldora and the prison to analyze the sealing magic, though actual liberation happened later. Physical characteristics transformed through power growth and racial evolution. The slime form expanded from 40 cm to 80-100 cm in diameter, shifting color to metallic or golden during specific skill activations or racial changes. After absorbing deceased human Shizue Izawa, Rimuru gained a humanoid form modeled after her appearance, featuring distinct silver-blue hair and golden eyes. This form matured progressively: initially manifesting as a 120 cm child, then gradually developing to 155 cm after becoming an Ultimate Slime. The humanoid form remained androgynous, lacking biological sex characteristics, with clothing generated from magic energy. Rimuru's canonical gender identity is genderless, consistent with slime physiology. While past life memories involved male self-identification, Rimuru currently identifies as neutral. Pronoun choices in adaptations do not reflect this genderlessness. Personality merges Satoru Mikami's human pragmatism with monster instincts. Core drives include a desire for convenience, peace, and communal comfort, motivating efforts to build the monster nation Tempest. Rimuru demonstrates strategic cunning, often employing deception, memory manipulation, or forged records to preserve a benevolent image while pursuing political objectives. Diplomatic resolutions are preferred, but threats to allies or subordinates provoke extreme ruthlessness, including torture, assassination, or large-scale warfare. Emotional bonds strongly connect Rimuru to those linked by naming or loyalty, triggering violent overreactions to their harm. Leadership duties gradually reduced initial naivety, though tendencies toward overwork and reluctance to refuse requests persisted from Satoru's corporate life. Abilities expanded via predation, evolution, and analysis. The core skill Predator enabled consumption and mimicry of organisms or objects, evolving into Gluttony and later Gluttonous King Beelzebub, capable of absorbing souls and skills. The analytical skill Great Sage offered constant cognitive support, ultimately evolving into the Manas Ciel, granting instant analysis and replication of observed abilities like space-time manipulation. Ultimate Skills such as Void God Azathoth provided reality-warping capabilities, including nihility energy manipulation and multidimensional barriers. Racial evolutions—from slime to Demon Slime after becoming a True Demon Lord, then to Ultimate Slime—multiplied magicule reserves and added spiritual body transformation. Combat proficiency incorporated sword mastery trained by Hakurou, magic absorption from Ingrasia's libraries, and original techniques like Megiddo (focused sunlight beams). Later capabilities included Turn Null energy generation, spacetime control enabling time travel, and clone creation. Interactions across media contributed to development. In spin-offs like *The Slime Diaries*, Rimuru participated in cultural exchange and daily governance, emphasizing community building. The OAD series *Rimuru’s Glamorous Life as a Teacher* depicted educating Shizue's former students, showcasing mentorship and Shizue's legacy. During the OVA *Visions of Coleus*, an undercover investigation in the Coleus Kingdom utilized disguise, intrigue, and human-world memories. The film *Scarlet Bond* explored loyalty themes through Benimaru's backstory. Main series events demonstrated moral compromises, such as sacrificing 10,000 humans to evolve into a True Demon Lord and revive slain subordinates after the Falmuth invasion. Leadership evolved from direct problem-solving to delegation to subordinates like the primordial demons.