After becoming a Demon Daki grew strong enough to kill and eat seven Pillars and gained the attention of Muzan Kibutsuji who allowed them to join the Twelve Demon Moons. She later dies after being beheaded by Zenitsu Agatsuma and Inosuke Hashibira.
Daki | Demon Slayer: Kimetsu no Yaiba S2 Ep.
Gyutaro was decapitated by Tanjiro with an assist from Tengen, while Daki was beheaded by a joint attack from Zenitsu and Inosuke.
Inosuke joins Zenitsu in killing Daki.
Fortunately, Zenitsu was able to single handedly beat the Upper Moon 6. Not only did he defeat the demon, he also created a seventh form called the Flaming Thunder God. These are the demons who have been given the title of Upper Moon 6 in Demon Slayer.
It has been said that no one has been able to kill an Upper Moon in a hundred years, since Upper Moon Six Daki and Gyutaro were killed. ”The demons with Muzan's thick blood coursing through them are demons that have gained a massive amount of strength from Muzan himself.”
After the deaths of Daki and Gyutaro, Kaigaku was promoted to become Upper Moon Six of the Twelve Demon Moons due to his power and confronted Zenitsu as a rematch he always desired.
While Daki expresses extreme devotion and submissiveness to her demonic master Muzan, she is also highly prideful to anyone she deems below her. This pride extends to the people that she eats as well. She will only eat beautiful people and kill them without eating them just because they annoy her.
At some point, Daki fought, killed and ate seven Hashira. Two days before Tanjiro Kamado and company infiltrated the Entertainment District, Daki was confronted by Omitsu, the manager of the Kyogoku House, over her mistreatment of the staff.
Nezuko setting Tengen on fire. By the end of the battle, Gyutaro's poison has spread throughout Tengen's body resulting in his inability to speak. As he lays dying from the poison, Nezuko Kamado intervenes and uses her her Blood Demon Art to burn the poison out of his system, allowing him to rejoice with his wives.
Muzan is shown to have a positive master-servant relationship with Daki, as the young Demoness seemingly worships and admires the Demon Progenitor immensely, fervently hanging on each and every one one of his words and doing her absolute best to accomplish the tasks he gives her.
Daki was obsessed with beauty and if she saw a beautiful human, she immediately grew the need to eat them. With the help of her Obi, Daki would trap her prey and store them inside the Obi. This allowed Daki to consume the trapped people at her leisure.
Given that she survived the Final Selection, she has excellent combat abilities. But Nezuko single-handedly overwhelmed Daki, showing just how strong she is as a demon. Therefore, it can be assumed that Nezuko would be able to beat Aoi if the two engaged in combat.
But the crowning moment of his achievements is when he epically slices off Daki's head and makes a run for it—after all, she won't die until her brother's head is also sliced. Unfortunately, Gyutaro spots Inosuke and stabs him right through where his heart should be with a sickle imbued with deadly poison.
Shinobu Kocho is a capable Demon Slayer whose worthy of being the Insect Hashira. That being said, she's arguably the weakest Hashira when it comes to pure strength.
Warning: This section contains spoilers from the Demon Slayer manga. Well, you'd be delighted to know that Tengen Uzui doesn't die fighting against Gyutaro and Daki. However, the Sound Hashira does die in the manga, but that happens far in the future.
Does Muzan have a favorite demon? Despite the fact that Muzan. is always shown to have disdain for his creations, Muzan does in fact have a favorite. On that list is Naki, made due to a convenient blood demon.
Why is Daki weak? Daki only seemed weak because she was fighting against 3 dudes that are Hashira level and one that is above that. Tanjiro, Inosuke and Zenitsu aren't Hashira level.
The only two people she really cares for are Muzan Kibutsuji and her older brother. She shows deep respect for Muzan Kibutsuji immediately falling into a bow when he appears. Although she cares and loves her brother she is seen insulting and blaming him at times when things aren't going well.
Her background as a courtesan coupled with her beauty meant that she would serve as a great and reliable source of income for Muzan, which is why the Demon King decided to be tolerant of her apparent stupidity.
Muzan Kibutsuji
Daki is faultlessly loyal to Muzan to the point at which it's almost obsessive. She drops her usual prideful demeanor around him and will act very meek when talking to him, seemingly transfixed by his prescience.
Zenitsu crushing on Nezuko. Upon seeing her for the first time, Zenitsu falls in love with Nezuko at first sight. She apparently views Zenitsu as a "weird dandelion" and did not initially seem to reciprocate his feelings. Although the two are rarely seen interacting together, Zenitsu treats her with affection and care.
It's implied that the characters from the original series have all since died and have been reincarnated in modern day Tokyo in the final chapter of the series, but two key characters confirm that Nezuko Kamado and Zenitsu Agatsuma eventually did have a family together as their great grandchildren, Yoshiteru and Toko ...
Nezuko Kamado
Zenitsu also protects Nezuko multiple times when she is in danger, evident during Zenitsu's first meeting with Inosuke Hashibira and the battle against Enmu in the train. Eventually Zenitsu and Nezuko would marry and start a family as evidenced by their descendants.