Unaired special of “Himouto! Umaru-chan” included with the manga’s tenth compiled volume. Realizing it is Taihei's birthday, Umaru asks Nana for advice on what to do for him. Umaru decides to act like an ideal sister and spend time with Taihei, only to discover that he prefers her the way she is. Later, as the girls begin their summer vacation by going to a swimming pool, Umaru wonders if she should stop putting on an act in front of her friends and reveal that she, Komaru, and UMR are the same person. As Umaru becomes conflicted over what will happen if she tells everyone, her friends assure her that she doesn't need to reveal her secrets if it'd just make her suffer. Relieved by the support of her friends, Umaru makes the decision to continue hiding her secret.
| Actor | Role |
|---|---|
 Aimi TanakaUmaru Doma (voice) | Umaru Doma (voice) |
 Kenji NojimaTaihei Doma (voice) | Taihei Doma (voice) |
 Akari KageyamaNana Ebina (voice) | Nana Ebina (voice) |
 Haruka ShiraishiKirie Motoba (voice) | Kirie Motoba (voice) |
 Yurina FurukawaSylphinford Tachibana (voice) | Sylphinford Tachibana (voice) |
 Hiroki MaedaYukio Takematsu (voice) | Yukio Takematsu (voice) |