People are not always who they appear to be, as is the case with Umaru Doma, the perfect high school girl—that is, until she gets home! Once the front door closes, the real fun begins. When she dons her hamster hoodie, she transforms from a refined, over-achieving student into a lazy, junk food-eating otaku, leaving all the housework to her responsible older brother Taihei. Whether she's hanging out with her friends Nana Ebina and Kirie Motoba, or competing with her self-proclaimed rival Sylphinford Tachibana, Umaru knows how to kick back and have some fun! Himouto! Umaru-chan is a cute story that follows the daily adventures of Umaru and Taihei, as they take care of—and put up with—each other the best they can, as well as the unbreakable bonds between friends and siblings.

Episodes included in the manga's seventh and tenth volumes.

While reveling in the successful clinching of a prized vase for his collection, Yoshifumi Nitta, a yakuza member, is rudely interrupted when a large, peculiar capsule suddenly materializes and falls on his head. He opens the capsule to reveal a young, blue-haired girl, who doesn't divulge anything about herself but her name—Hina—and the fact that she possesses immense powers. As if things couldn't get any worse, she loses control and unleashes an explosion if her powers remain unused. Faced with no other choice, Nitta finds himself becoming her caregiver. To let her use her powers freely, Nitta asks Hina to help out with a construction deal, which goes smoothly. But while this is happening, a rival yakuza group covertly attacks his boss. To Nitta's shock, his colleagues later pin the blame on him! Tasked with attacking the rival group in retaliation, Nitta steels himself and arrives at their hideout. But suddenly, Hina unexpectedly steps in and helps him wipe out the entire group. As it turns out, Hina might just become a valuable asset to Nitta and his yakuza business, provided she does not use her powers on him first! And so the strange life of this unusual duo begins.

Umaru Doma is a model student who has a hidden side: when she gets home each day, she puts on her hamster hoodie and turns into a sluggish otaku fond of junk food. As Umaru continues these daily antics, the friendship between her and her classmates—Nana Ebina, Kirie Motoba, and Sylphinford Tachibana—deepens, and more and more interesting events begin to unfold. Of course, these events give rise to numerous questions. What did Nana ask of Umaru's brother Taihei? Who is the mysterious girl with the diamond hairpin? And most important of all: why does this girl seem to know Umaru? These questions and more will be answered in Himouto! Umaru-chan R!