"Umaru and Her Rival" (うまるとライバル Umaru to Raibaru?) is the fourth episode of the Himouto! Umaru-chan Himouto! Umaru-chan (Himouto! Umaru-chan (Anime)).
Umaru goes to the game arcade as UMR and begins to obtain large amounts of dolls from the crane machines, despite numerous attempts from the staff to sabotage her. That night, she shows her huge collection to her brother.
At school, Umaru and her friends play a messed-up game of tennis, where Sylphynford tries to defeat her; Kirie also displays her prowess, while Ebina keeps screwing up. Umaru eventually becomes utterly tired from the ordeal.
Taihei gets a cat ornament from Alex and promises him to take care of it. He shows it to Umaru (who says it's ugly) and warns her not to mess with it, but as usual, she doesn't listen. After using it and her hamsters in a Pokémon parody, she breaks it by accident. Fearing that her brother won't buy her anything again, she becomes her outside self and attempts to fix the ornament, but panics when she can't remember what its face looks like. When her brother returns home, she admits her mistake (which her brother forgives)... and is forced to reveal that she bought the stuff to fix it with his credit card (angering him).
Umaru then takes her brother back to the arcade (where the rock-paper-scissors contest was held earlier) where they're holding a Space Stream Fighter IV fighting game tournament. Alex shows up as well, and as he and Taihei talk, the contest begins, and UMR and all other contestants are introduced (such as manga artist SKH, meaning Sankaku Head, the series' creator) as well as Sylphynford (who declares she will take first place), who is told by the staff to wear a mask and not use her real name, but she ignores them. The girls face off until Alex (who's actually Sylphyn's brother) sees her. Embarrassed, she runs away, and UMR wins by default. As Sylphyn runs from the building, Alex catches her. The next day, Sylphyn surprises Umaru, declaring she will surpass her on the day's test.
- The arcade that UMR visits, "PLAZA GAPCOM" is a reference to "PLAZA CAPCOM", a chain of arcades centers in Japan operated by video game company, Capcom.
- Inside the arcade, one of the games is "Space Stream Fighter IV", a referecene to Street Fighter IV, which was created by Capcom.
- One of the games there is a reference to Taiko no Tatsujin, a game designed to simulate taiko drumming.
- The figure that UMR wins is Hatsune Migu, which is a reference to Vocaloid character, Hatsune Miku
- While daydreaming at her tennis class, a picture of Umaru in front of a space swirl wearing glasses and the caption "(x)zuka Zone" while holding her racket is shown. This is in reference to the "Tezuka Zone" a technique used by Kunimitsu Tezuka from the series, Prince of Tennis.