Female. In public, she is a popular high school girl who is perfect in academics, sports, looks, and personality. At home, she is highly dependent on her brother, Doma Taihei, constantly making him run errands. If he doesn't buy her what she wants, she throws a tantrum to get her way. She loves games, anime, and manga. While her personality is cute, she can be lazy and self-centered. In public, she has the aura of a perfect, top-tier beautiful girl, always neat and flawless. At home, she wears an orange hamster hoodie and transforms into a small, SD-style character. She is round, cute, acts aegyo-filled, and pouts often. She is soft-hearted and keeps two hamsters.

Female. A wealthy, mixed-race young lady with long blue hair, blue eyes, and yellow cross-shaped pupils. She views Doma Umaru as her rival and constantly challenges her. She is good at both studying and gaming but often loses to Umaru. She has a lot of pride but is often a klutz, leading to many funny moments.

Female. Known as Ebina, she lives in the apartment below Umaru. She has a very large chest and brown hair. She is a beautiful girl with a generally gentle and warm vibe. She is extremely kind but also quite timid. She loves eating very much. Since she is from the countryside, her dialect sometimes slips out. She is a close friend of Umaru and has a crush on Doma Taihei.

Female. Takeshi Motoba's younger sister. She has long black hair and sharp eyes. On the outside, she seems scary and taciturn, but she is actually incredibly shy and kind. She has trouble talking to anyone who isn't a child and gets nervous easily. She mistakes Umaru (in her home form) for Umaru's younger sister (naming her Komaru) and treats her as a master. She does not call the beautiful public Umaru her master. She loves cute things.

Male. A plain office worker with black hair and glasses. He is neat, diligent, and very kind with a strong sense of responsibility. He nags a lot but basically puts up with everything. He handles all the housework and takes care of Umaru while working his job. He is a pro at daily life skills like cooking and cleaning. He is one of the few people who knows about Umaru's double life. He is Umaru's older brother and guardian figure. Though he is often pushed around by his sister, he takes great care of her. He has been friends with Takeshi Motoba since their student days.

His basic facial features resemble Doma Taihei. He has an afro hairstyle and a beard. He is a lazy office worker who hates working. He is a total pushover for his younger sister. He is Taihei's colleague and has been close friends with him since school. He is the "sloppy version" compared to Taihei. He is Kirie Motoba's older brother. He has never had a girlfriend and is one of the few who knows Umaru's home form. He thinks Umaru (in SD form) is cute and calls her 'Tanuki'.