Umaru, a beautiful high-school student, appears to be the epitome of a perfect and accomplished teenager, but she leads a secret double life. Once she returns home, she transforms into a slovenly, junk-food-eating, video-game-obsessed slob. Her over-taxed older brother Taihei is the only one who witnesses this unsavory side of Umaru, and he tirelessly juggles his responsibilities while trying to get his younger sister to abide by society's norms. Despite finding herself in peculiar circumstances and befriending new acquaintances, Umaru will persist in her quest to indulge in all-night anime binges and chip-munching sessions.