Even for a Demon Slayer, Inosuke’s new companions are a startling revelation, but these unexpected allies may be more vital than they appear.
Things are still intense in Demon Slayer: Kimetsu no Yaiba, but things became quite strange in Season 2 Episode 11. Inosuke Hashibira says he’s had enough of these stealth games after Zenitsu Agatsuma vanishes, forcing Tengen Uzui to abort the operation. Throwing himself headfirst through the ceiling to gain access to the attic, for how else would he, Inosuke utters some strange words: “Hey mice! My swords! These two very muscular mice, who walk upright and who, indeed, bring Inosuke his swords.
Muscle mice are precisely what their name implies: extremely well-built rodents. Most Corps members are escorted by a Kasugai crow who issues instructions from Ubuyashiki, so animal assistance is not rare in Demon Slayer. Inosuke, on the other hand, wanted to eat the crow that was assigned to him, demonstrating that he doesn’t get along with animals.. Yet, unsurprisingly, he’s totally in love with muscle mice and wants to have his own miniature minions to lead them.
Tengen Uzui’s Muscle Mice are his servants, and it appears that he handed Inosuke a pair of them for their task in the Entertainment District. Given that they each wear a gem-encrusted headband identical to Sound Hashira’s, the mice evidently belong to Tengen rather than the Demon Slayer Corps. Although he dubs the Muscle Mice “the Corps of Shadow Demon Slayers”, it’s highly unlikely anyone else would consider them to be true members of the Corps.
It is implied that the muscle mice are nothing more than field mice that Tengen has trained to act as his “ninju”. The flashy Hashira demands as much theatricality from them, and only accepts mice who will be narcissistically proud of their outrageous musculature. In fact, “muscle” seems to be the only word mice can say. How Tengen manages to make these mice so muscular, make them walk on two legs, make them understand human language and even make them talk is a mystery comparable to the origins of Muzan Kibutsuji, but it is probably less likely that he be one day explained.
The pumped-up mice who work behind the scenes to help Demon Slayers slay demons are far too weird to be brought in for such a trivial task as delivering swords. Tengen mentions during the Taisho-Era Secret segment that he summons the mice to creep into the little places he can’t go. Daki, High-Rank Six, whom Tengen has been looking for, has already shown that she can escape through walls and ceilings inside houses in the Recreation District. If she tries again to escape in this way, it is none other than the muscular mice who will be able to find her.
Muscle mice have enormous strength beyond what their cartoonish muscles are capable of, and while they probably can’t fight a demon, they might find a way to help. These mice will most likely stay present for the duration of Tengen Uzui’s “Entertainment District” arc, as they appear briefly in the opening credits. The muscle mice may not be able to kill Daki on their own, but it’s still exciting to imagine that these strange rodents will play a significant role in the Demon Slayer sequel.