WARNING: The following contains spoilers for Demon Slayer: Kimetsu no Yaiba Season 2, Episode 17, "Never Give Up," now streaming on Funimation, Hulu and Crunchyroll.
Tanjiro, Inosuke and Zenitsu had no idea what they'd gotten themselves into when they volunteered for Tengen Uzui's mission at the start of Demon Slayer: Kimetsu no Yaiba's "Entertainment District" arc. The boys joined the Sound Hashira in the city of Yoshiwara to locate Tengen's missing wives and managed to draw out Daki and Gyutaro, the demon siblings who share the title of Upper-Rank Six. Ordinarily, only a Hashira would have even a one-percent chance of surviving a fight with an Upper-Rank. And yet, Tanjiro, Inosuke and Zenitsu looked like Hashira themselves as they played a critical role in the fight, each delivering the final blows for the first death of an Upper-Rank in 100 years.
The Hashira of the Demon Slayer Corps are the best of the best -- swordsmen with skills beyond compare in the fight against Muzan Kibutsuji's demons. While the late Kyojuro Rengoku joked there were 10,000 steps to becoming a Hashira, the path to the Corps' highest rank is relatively simple. In order to become a Hashira, a Demon Slayer who is ranked at Kinoe -- the highest non-Hashira rank -- must kill either 50 demons or a member of the Twelve Kizuki. The only other method is to become a Tsuguko (apprentice) to a Hashira, whom that Hashira can name as their replacement should they live long enough to retire.
Tanjiro, interestingly, would already be a Hashira if he'd been ranked at Kinoe when he killed Enmu, Lower-Rank One of the Twelve Kizuki, during the "Mugen Train" arc. Unfortunately, Tanjiro, as well as Inosuke and Zenitsu, are only Kanoe -- not even halfway to the top of the Corps' ranking system. This bizarre technicality that prevents Tanjiro from being the Sun Hashira is likely for this exact scenario, preventing someone like Tanjiro from becoming a Hashira before they're ready. After all, the Hashira are assigned large areas to patrol and must be relied upon to kill scores of demons and save lives efficiently -- something Tanjiro is still too weak and inexperienced to do.
While Tengen Uzui did declare to Gyutaro that the boys were his brilliant Tsuguko, it's unclear if he truly claimed them or just said that to hype them up after their flashy entrances. Assuming Tengen, or any of the boys for that matter, survived Gyutaro's Blood Sickle explosion (or his poison), they might just find themselves on the path to becoming Hashira if Tengen officially names them his Tsuguko. Tanjiro, Inosuke and Zenitsu would surely welcome being Tengen's Tsuguko, as Tengen reminds Tanjiro of Rengoku while Inosuke has begun to use the word "flashy" as well. Zenitsu, on the other hand, isn't the biggest fan of the Sound Hashira, but he would likely want to stay with Tanjiro and Inosuke regardless.
Tanjiro, Inosuke and Zenitsu have proven they have Hashira potential, even if their victory over Daki and Gyutaro deserves an asterisk. By Upper-Rank standards, Daki is so pitifully weak as to be undeserving of the title she shares, so Zenitsu and Inosuke's victory over her, while impressive, feels like only technically beating an Upper-Rank. Tanjiro, meanwhile, would have been killed by Gyutaro several times over if Tengen had not repeatedly saved him and done the bulk of the work fighting the true Upper Six demon. While Tanjiro's beheading of Gyutaro is no small feat, he never would have accomplished it without the opening that Tengen sacrificed his body to create.
While Sun Hashira, Beast Hashira and Thunder Hashira all have a nice ring to them, the boys still have a long way to go. Still, that they've survived several encounters with members of the Twelve Kizuki while earning the respect of Kyojuro and Tengen speaks to their prodigious talent. Multiple Hashira have complained that the Demon Slayer Corps is getting weaker with each new recruit, so Tanjiro, Inosuke and Zenitsu might just be the greatest hope the Corps has left in continuing the battle against the flesh-eating demons that plague Japan. After their heroics in the "Entertainment District" arc, Tanjiro, Inosuke and Zenitsu should have climbed a few spots in the Corps' ranking system, at the very least.