The anime's story centers around Taihei Doma and his little sister Umaru, who boasts beautiful looks as well as prowess in both school and sports. However, she has a certain secret. Everyone may think she is the ideal girl, but she is anything but. "Himōto" is a pun on "imōto" (little sister) and "himono," which means "dried fish," but in slang can refer to a woman who is proper in public but lazy at home.

(Source: ANN)