High-school beauty Umaru seems like the perfect teen wunderkind, but she's hiding a shocking double life. As soon as she gets home, she becomes a junk-food-inhaling, soda-guzzling, video-game-addicted slob. The only one who sees this unsavory side of Umaru is her beleaguered older brother Taihei, who does his best to keep up with his work while trying to get his little sister to behave like a decent member of society. As she makes new friends and gets into a number of wacky situations, Umaru will continue to fight for her right to stay up all night binging potato chips and anime.