Rimuru Tempest began life as Satoru Mikami, a 37-year-old Japanese salaryman whose life ended shielding a colleague from a stabbing. Reincarnated in a fantasy realm as a slime, unique abilities manifested from his final wishes: "Predator" to devour and analyze targets, and the cognitive assistant "Great Sage." Early existence involved bonding with the sealed Storm Dragon Veldora. A pact exchanging names freed Veldora into Rimuru's stomach, granting the dragon's affinity and the surname "Tempest." Initial encounters saw Rimuru aiding goblin tribes, negotiating with dwarven kingdoms, and integrating diverse monsters like ogres and direwolves. Naming these monsters spurred their evolution but forged soul-linked lineages, unintentionally creating a loyal faction. Absorbing the adventurer Shizu yielded a human form—androgynous with silver-blue hair and golden eyes—enabling movement in human societies. This act inherited Shizu's mask, her final will, and the unstable spirits plaguing her. Physical form evolved significantly. The slime body expanded from 40 cm to 80–100 cm diameter, shifting from translucent blue to metallic or golden under defense. Human appearances visually aged: initially 6–7 years old (120 cm), progressing to 9 years (130 cm) after absorbing the Orc Lord, then 12–13 (140 cm) as a True Demon Lord, and finally an androgynous adolescent (155 cm) as an Ultimate Slime. Rimuru is biologically genderless and sexless, consistent with slimes in this world. Mentally retaining Satoru’s male identity early on, Rimuru gradually adopted a neutral gender identity, expressing both masculine and feminine social behaviors without physical sexual characteristics. Author Fuse confirmed this gender neutrality, noting adaptation pronoun misuse stems from translation errors. Abilities grew through combat and assimilation. "Predator" evolved into "Gluttony" after defeating the Orc Lord, then into the Ultimate Skill "Beelzebuth" post-demon lord ascension, enabling soul absorption and matter decomposition. "Great Sage" evolved into "Raphael" and later the sentient "Ciel," providing advanced analysis, spell creation, and time-altering perception. Key combat skills included "Poisonous Breath," elemental fusions like "Black Flame," and strategic large-scale magic such as "Megiddo," harnessing sunlight for precision strikes. Demon lord transformation during the "Harvest Festival" multiplied magicules tenfold and granted immortality. Later evolutions unlocked reality-warping capabilities. Personality blended Satoru’s pragmatic human outlook with slime adaptability. Typically kind, diplomatic, and conflict-averse, Rimuru often accepted excessive burdens due to reluctance to refuse requests. Yet, threats to allies or subordinates provoked ruthless retaliation, including torture or annihilation of enemies. Leadership merged urban development expertise from Satoru’s career with manipulative tactics—revising historical records, erasing memories, or leveraging blackmail to uphold Tempest’s image. Inherent anxiety and self-doubt initially caused underestimation of personal authority, gradually shifting toward calculated confidence. Spin-offs like *The Slime Diaries* highlighted nurturing, humorous facets, such as organizing festivals or mentoring students in OADs. Rimuru's world role centered on founding the Jura Tempest Federation, a monster nation championing human-monster coexistence. Political influence expanded through alliances with kingdoms like Dwargon and the Sorcery Dynasty Thallion, culminating in recognition as an "Eight Star Demon Lord." Leadership involved delegating to potent subordinates, including primordial demons like Diablo. Crises forced moral compromises—sacrificing 20,000 Falmuth soldiers to evolve into a True Demon Lord and resurrect slain citizens. Later arcs saw Rimuru consolidating power as the sole "Great Demon Lord," managing inter-nation diplomacy, and confronting threats like the Eastern Empire. Key relationships featured Veldora as a best friend and confidant, Shizu as a spiritual predecessor, and subordinates treated as family. Bonds with beings like the ogre chieftain Benimaru or the primordial Diablo cemented loyalty through naming and shared purpose. Antagonists such as the Western Holy Church’s Hinata Sakaguchi later became uneasy allies after initial conflicts, reflecting Rimuru’s capacity for pragmatic forgiveness. Media expansions explored these dynamics: the film *Scarlet Bond* involved aiding a cursed kingdom, while the OVA *Visions of Coleus* featured undercover missions in human societies. Overall narrative development traced a path from passive observer to proactive ruler. Early naivety in human-monster relations led to tragedies like Shion’s death, prompting strategic ruthlessness. Later reliance on subordinates allowed focus on governance, while abilities like "Ciel" enabled complex multiversal interactions. Across all media—films, OADs teaching magic academies, and spin-offs—Rimuru’s core goal persisted: creating a convenient, peaceful world, balancing human empathy with monstrous power.