"Umaru's Birthday" (うまるの誕生日 Umaru no Tanjōbi?) is the sixth episode of the Himouto! Umaru-chan Himouto! Umaru-chan (Himouto! Umaru-chan (Anime)).
It features several plotlines (Umaru dealing with a cola shortage, the siblings and Kirie playing a board video game, Taihei making him and Umaru separate rooms as a result of Umaru annoying him too much, and Umaru upset that her brother has a day off, but she has to go back to school), the last of which depicts Umaru's birthday (September 26). Onii-chan appears not to remember this, and while Umaru at first assumes this is just him pretending, she gradually starts to wonder if he has indeed forgotten all about her birthday, worrying her. In the end, though, she runs home and catches him decorating the room for her birthday, leaving him slightly embarrassed.