Demon Slayer's "Entertainment District" arc saw the flashy Sound Hashira Tengen Uzui taken to his limits in his battle with Upper Moon Six, the demon siblings Gyutaro and Daki. The movie-level animation quality for Tengen's action sequences brought to mind the beautiful swordsmanship shown off by the starring Hashira of Demon Slayer: Mugen Train: Kyojuro Rengoku.
Even after his death, Rengoku's influence and impact on the Demon Slayer cast and fan base is still felt. The Flame Hashira exuded a level of kindness, power and self-sacrifice that made him beloved by everyone, who all wish for more of the great Rengoku. What would've happened if he somehow survived his encounter with Akaza and replaced Tengen as the main Hashira in the Entertainment District? Specifically, how would Rengoku have done in a fight with Gyutaro and Daki compared to Tengen?
Rengoku's Advantages Over Tengen in Demon Slayer
Rengoku was widely regarded as one of the finest Hashira, even by his peers. Tengen Uzui is among the most vocal admirers of Rengoku's abilities, expressing dismay that, "even Rengoku couldn't defeat an Upper Moon," and calling out to his spirit for advice at the end of Season 2, Episode 15.
Rengoku's natural talent, and his birth into a long lineage of Flame Breathing masters, made him an expert in not only the Flame Breathing techniques, but also a physical beast who could keep up with the most powerful demons. During their grand battle, Akaza constantly praised Rengoku's reflexes while the two fought at speeds so fast that Tanjiro failed to follow their movements.
While Tengen was a combat expert in his own right, with his dual Nichirin blades and bag of explosives, his feeling of inferiority to Rengoku shows just how amazing the Flame Hashira was. Rengoku put on an impressive showing against Upper Moon Three Akaza, all on his own, while Tengen barely won with his life against Upper Moon Six -- even with the help of Tanjiro, Zenitsu and Inosuke. Using his superior speed and wide arsenal of multipurpose breathing techniques, Rengoku would likely fare better at defending himself from Gyutaro's and Daki's blitz than even Tengen did.
Why Rengoku Would Ultimately Lose to Gyutaro and Daki
While Rengoku possibly edges out Tengen in raw combat ability, Tengen's physical advantages and unique Musical Score Technique made him the perfect Hashira to take on Gyutaro. His poison resistance built up from his shinobi training kept him in the fight long after being cut by Gyutaro's poison blades. And his Musical Score Technique allowed him to perfectly read and counter Gyutaro's movements -- even after losing an arm.
Without poison resistance, Rengoku's defense would have to be perfect, a near-impossible task considering he'd have to fend off both Gyutaro's blinding speed and Daki's dozens of Obi. Tengen also had access to an additional blade to use, as well as explosives that he employed to boost his defense. Rengoku would be armed with solely his sword, giving him even less room for error.
If Rengoku were able to fight Gyutaro and Daki with the same help that Tengen had from a relentless Tanjiro, Zenitsu and Inosuke, there would be a chance Rengoku could pull out the victory using his swordsmanship and breathing mastery. However, Tengen was the better matchup to deal with Gyutaro's poison blades. Even if Rengoku managed to seal a win, he would likely give his life in process -- a brutal scene Demon Slayer fans wouldn't enjoy watching for a second time.