Every story arc in Demon Slayer brings one or more great new foes, and by this stage, protagonist Tanjiro Kamado has gained the strength to face and defeat fearsome Upper Moon monsters. The last few storylines have brought some elite enemies to truly test the hero, and Season 3's "Swordsmith Village" narrative introduced two more Upper Moons in Hantengu and Gyokko – but only one of them is delivering.
Hantengu is the Upper Moon Four, taking on many adversaries and winning, while Gyokko, the vase-themed Upper Moon Five, was a huge letdown. He did had Muichiro Tokito on the ropes for a little while, but Mist Hashira employed frustratingly simple shonen tactics to humiliate Gyokko and finish him off for good. Here's why Upper Moon Five was Demon Slayer's most underwhelming new foe.
Gyokko Was Defeated Too Easily in Demon Slayer
For several episodes, the formidable Gyokko had faced Muichiro and the residents of Swordsmith Village, wreaking havoc with his fish and octopus-themed assaults while Hantengu kept Tanjiro and Genya occupied elsewhere. While Gyokko's fight had some fantastic moments (the Upper Moon Five has some very impressive strength), it seemed disappointing overall. Even though he almost killed Muichiro and was Muzan's favourite, the outcome was too simple. He and Muichiro merely took turns upping the ante with more powerful moves, including Gyokko's "this isn't even my final form" moment when he transformed into a mer-man with muscular arms and diamond-hard scales.
Gyokko lost because Muichiro beat him at his simple game, with the Mist Hashira having a cliché "I'm finally taking this seriously" moment and executing the winning move. He didn't even need any special tricks or advanced tactics to win; he just used a powerful move. Gyokko didn't even have a new trick to keep his vulnerable neck safe, so he got casually decapitated like any ordinary demon and crumbled away.
By contrast, Enmu, Demon Slayer's Lower Moon One, truly challenged Tanjiro and Inosuke with his train-body, dream powers and tentacles, which made Tanjiro's final victory feel earned. Daki and her brother Gyutaro, meanwhile, were an incredible tag-team who had to be decapitated simultaneously, which posed an incredible challenge for even the mighty Tengen Uzui. But Gyokko died from one decapitation strike from Muichiro, who only had the benefit of his demon slayer mark and an advanced Mist Breathing form. It was shonen combat at its worst, featuring two fighters taking turns until one of them had no more cards to play.
Gyokko Was Unconnected to the Heroes of Demon Slayer
Gyokko was also a personal disappointment. He had no backstory or flashbacks to explain how and why he became a monster. Minor foes such as the hand demon and Kyogai had similar scenes. On the one hand, this makes Gyokko appear disturbingly enigmatic and otherworldly. Demon Slayer, on the other hand, could have countered with a more nuanced demeanour and cryptic hints about his origins. Gyokko had a clear "evil for evil's sake" demeanour, which made him appear shockingly superficial in comparison to the Daki/Gyutaro pair or even Kyogai and Rui.
Gyokko also had no personal ties to any other Demon Slayer character, whether they friend or foe. Other demons, such as Akaza and Doma's rivalry or the hand demon killing Sakonji Urokodaki's students in the past, have a greater impact on the plot since they have personal business with someone else. Gyokko actually feels like a stand-alone character, implying that he was a boss battle for the sake of boss battles. Most shonen characters have at least one villain that exists just to provide combat scenes, and Gyokko had that role in Season 3 of Demon Slayer.
It's disappointing too, since Demon Slayer usually has a "quality over quantity" approach to its characters, as opposed to bloated shonen casts in the likes of Bleach and Fairy Tail. It makes Gyokko conspicuous for all the wrong reasons, a simple boss battle monster who lost because his final form wasn't good enough.