Umaru and Oniichan (うまるとお兄ちゃん Umaru to Onīchan?) is the the first chapter of Himouto! Umaru-chan Himouto! Umaru-chan (Himouto! Umaru-chan (Manga)).
A responsible, weak-willed, spineless, hardworking man makes it his mission in life to refine his strange (and strangely perfect) younger sister whose true, secret personality is a chibi otaku slacker; an irresponsible, spoiled, selfish, manipulative crybaby who will do anything and everything to get her way, including using and abusing her brother.
The chapter begins with a description of 16-year-old Umaru Doma, a high school girl who's all-around perfect. However, that's only when she's outside. At home, however, she shrinks down to her true form, the "himouto": a worthless lazy-bum sister. At night, her hardworking older brother, Taihei, calls Umaru to dinner, but Umaru tells him to feed her. Taihei yells at her to get to the table. Umaru complains that the fried rice is cold, but Taihei responds that she didn't get to the table fast enough. She then says that they're supposed to eat bread on Tuesdays, and Taihei responds, "It's Monday." Umaru realizes that Weekly "Jumpu" (a parody of "Weekly Shōnen Jump") comes out today. "Last week's Jun Piece (which is a refrence of One Piece) had an awesome cliffhanger!" She begs him to buy it at the convenience store, but Taihei refuses because he's exhausted and tells her to just get it there tomorrow. Umaru responds, "If Umaru does that, Umaru's secret will be exposed! At school, Umaru's backstory is, 'My parents have forbidden me to read Himouto! Umaru-chan (Manga), so I'm unfamiliar with anything Jun Piece, but this reindeer character is adorable!'" Taihei asks where she came up with that, and she responds "Umaru has a reputation to protect. Lately rumors started flying; one such rumor is that Umaru reads poetry at her library". Taihei tells her that they live in a 1DK (1-room apartment), and again refuses and tells her that she'll get it tomorrow. Umaru responds by rolling around on her bed, throwing her first tantrum in the series: "NO WAY NO WAY NO WAY NO WAY; WANNA READ TODAY!!" Taihei realizes he has created a monster; it has been a year since Umaru moved in to his apartment and he has apparently been spoiling her ever since. Now she has become very impatient, selfish, and lazy. As we see Umaru rolled up in her blanket, Taihei continues thinking, "By the time she grows up, she won't be able to survive the real world!" Umaru then puts on her "Outside Face" to get Taihei to buy the magazine, but he refuses once again. After a moment of silence, Umaru starts crying and yelling: "WANNA READ WANNA READ WANNA READ WANNA READ WANNA REEEEEEEAD!!!" She loudly begs Taihei to buy her the magazine, but he tries to ignore her until he finally buys it. As Umaru reads her Jumpu, Taihei pleads for her to learn self-control and patience. Umaru apologizes and asks him to be quiet because "this is the best part". She then asks why he didn't get her potato chips while he was there, angering him. The next day, classmates ask Umaru what happened to her, and she claims that her brother scolded her, causing the others to complain about Taihei being a horrible brother. The chapter ends with Umaru being described as a terrible "himouto."
"This pretty little sister has her own secret!"