Duemouse is a supporting character in Duel Masters Versus Revolution Final, whose role is deeply intertwined with both the comedic and narrative elements of the season. His background from previous seasons informs his situation in this series. Originally introduced in Duel Masters Versus Revolution, Duemouse was the costumed mascot of a theme park called Duel Masters Land. Beneath the cheerful mouse suit was a being with a more complex nature, a robot named Chuujiro who was initially part of a scheme against the Duel Masters world. However, after being freed from this programming by the protagonist Katta Kirifuda, Duemouse developed a sense of honor and a firm belief that Duel Masters should be a fun game, not a tool for revenge.

By the time of Versus Revolution Final, Duemouse has become a recurring presence around Katta and his friends. A significant change has occurred: the original Duemouse entity is now just the mouse costume itself, and it requires someone to wear it to move around and support him. This leads to the character's most notable storyline in this season. To get close to Katta, a girl named Utsubomi Kazura volunteers to wear the Duemouse costume. The situation comes to a head in a humorous and pivotal episode when Katta forcibly removes the costume, revealing Utsubomi inside, which leads to a series of misunderstandings and Katta developing a crush on her.

Following this revelation, Duemouse continues to appear in a supporting capacity. He is shown to be helpful, such as when he finds the exhausted creature Katsuemon, a member of the Hamukatsu team, and brings him to Katta. He also participates in less serious, gag-driven episodes, for instance, acting as an announcer for a contest that pits various characters against each other for the role of the show's main hero. His personality remains consistent with his post-redemption self, showing loyalty and a sense of chivalry, in stark contrast to his sometimes scheming original persona. He does not possess notable combat or dueling abilities that define his role; instead, his function is primarily narrative, serving as a catalyst for character introductions, comic relief, and a link between the main cast and other events. His key relationship is with Katta, whom he respects and supports, and his role in the Katsuemon subplot demonstrates his helpful nature. The situation involving Utsubomi creates a complex dynamic, as the suit she wore is both a character and a tool, highlighting the unusual and playful nature of Duemouse's existence in the series.