Kurio Mifune, known in the English adaptation as Spritle Racer, is the younger brother of Speed Racer and the youngest child in the Mifune family. He is a mischievous, energetic boy around seven years old, recognizable by his short brown hair and black eyes. Throughout the story, Kurio provides the main source of comic relief, consistently injecting humor into tense situations. He is inseparable from his pet chimpanzee, Chim-Chim, and the two form a constant duo, frequently stowing away in the trunk of the Mach Five to follow Speed’s adventures. Despite his playful nature and tendency to cause trouble, Kurio is fiercely loyal to his older brother and possesses an uncanny knack for appearing at exactly the right moment to help Speed escape danger, often inadvertently acting as a secret weapon. His motivations are simple and heartfelt: a love of excitement and a deep desire to support his family. Key relationships include his admiration for Speed, his bond with Chim-Chim, and his place within the wider Racer household. While Kurio does not undergo dramatic character development, his consistent presence underscores the themes of family unity and lighthearted perseverance, and his ability to hide in small spaces and turn chaotic antics into unexpected rescues proves his value beyond mere comedy.