Popular shonen action anime Demon Slayer has a number of recurring themes and elements, including the "monster hunter" idea it shares with Chainsaw Man and Jujutsu Kaisen as well as the idea of having a small, elite corps for the heroes and villains. Demon Slayer's nine Hashira resemble Bleach's 13 Soul Reaper Captains in many ways and My Hero Academia's top 10 professional heroes in others, but there is one significant distinction between them.
The Hashira are regarded as humanity's best defense against demon-kind because they are by far the strongest demon slayer corps members. The nine Hashira, who are the elite of the demon slayer corps, are surprisingly humble and self-aware despite this not going to their heads. The Soul Reapers and professional heroes, on the other hand, grew too accustomed to ruling their own worlds and suffered as a result.
Why the Hashira Maintain Their Humility
Whether or not their leader Kaguya Ubuyashiki encouraged it, the nine Hashira have a modest and practical mindset as the top warriors in their organization. The Hashira are remarkably down to earth when compared to other anime elites, though they do have some pride and confidence in their tremendous abilities and veteran status. They maintain their integrity because they are aware of their disadvantage in the ongoing conflict with Muzan and the Upper Moons and that hubris is the last thing they need.
Excessive pride, complacency and arrogance will only hinder the Hashira further, and they get daily reminders of their fragile humanity. Most demon slayers die young, even the most skilled and talented ones, which reflects in the corps accepting 15-year-olds like Tanjiro into its ranks. Demon slayers are ultimately prey, even if they actively hunt demons with their Nichirin swords, and the Hashira are simply stronger prey. Kyojuro Rengoku, for example, can easily dispatch ordinary demons but lost his life fighting Akaza, while Tengen Uzui the ninja was injured to the point of early retirement when fighting Gyutaro. Obanai Iguro, the serpent Hashira, was somewhat concerned but not surprised or alarmed that after Tengen's victory, there were two gaps in the Hashiras' ranks.
The Hashira clearly strike a sensible balance between self-confidence and the humble awareness that they're almost as liable to die in battle as other demon slayers are, all without succumbing to despair or fear. It's a remarkable feat, with the Hashira being grimly conscious of their own human frailty and poor survival rate while also inspiring Tanjiro's squad with their immense power and prestige as shonen-style mentors. As other anime series recently showed, it's easy for the elite heroes to think themselves invincible and become too used to peace and victory, but not the Hashira. If they don't all get wiped out first, they're in a good position to fight Muzan and his minions with an honest and practical appraisal of their own power, which may give them the edge.
Hubris Cost the Soul Reapers & Pro Heroes Their Lives
Even though the nine Hashira aren't quite as strong as their pro hero counterparts in My Hero Academia or their Bleach Captain forebears, the Hashiras' modest self-awareness as weak, mortal people ensures that they don't get into fights they can't win and that they never foolishly underestimate their enemies. In contrast, after defeating the Quincy army a few centuries ago, the Soul Reapers in Bleach developed a strong sense of complacency and pride, with arrogance serving as their fatal flaw.
Ironically, the Soul Reapers' triumph resulted in their greatest weakness, the inability to uphold the peace they had previously worked so hard to achieve. That's a big part of the Wandenreich's incredible success so far in the Thousand-Year Blood War anime, and the Soul Reapers are just now waking up out of their complacency to start training in shonen-style combat. But several Captains, including Yamamoto himself, lost their lives as a result of their failure to learn this lesson.
The pro heroes in My Hero Academia had a similar problem. Unlike the humble Hashira, the pro heroes got too used to being the dominant and uncontested rulers of their world, and they greatly underestimated the numbers, Quirks and resolve of the many criminals and outcasts who hated them. This led to the Paranormal Liberation Front's creation -- a villain army that, with Tomura Shigaraki at its head, might just tear down hero society for good. The pro heroes were totally unprepared because they weren't used to a real challenge, and now many heroes have gotten themselves killed or quit their jobs entirely out of shame.
In the Demon Slayer universe, where everyone from the Hashira to the rookies is constantly reminded that they must go Plus Ultra and go all out if they hope to even survive, let alone rid Japan of demon-kind once and for all, such a thing would never happen.