Each and every demon shown in Demon Slayer has been portrayed with a tragic past that gets the viewers to sympathize with them and their transformation.
In many heartfelt situations, the demons need to be decimated and that freed their human conscience out of negative emotions that pushed them to a cursed fate of immortality.
In the Entertainment Arc of Kimetsu No Yaiba, the last episode that showed the flashback of the Upper moon six: Daki and Gyutaro in their human form portrays a lot of tragic realities about frail human nature and their bleak moralities.
Questioning Appearances and Beauty Standards
Daki was called Ume, her human name, and she was a beautiful child born into poverty that took her parents away.
Gyutaro was a poverty-stricken child, whose appearance was so unpleasant that people used to throw stones and jabs at him, so he resorted to begging and stealing his way around to survive.
Gyutaro showed his unconditional brotherly affection towards Ume and kept her warm in the winters.
He stick to her side like no other, and she grew into a beautiful woman.

One tragic night, when she was forcefully being touched by a stranger, she stabbed him in the eye which led her to meet a devastating fate.
She was burned alive for not consenting to submission and standing up for herself.
The heartbreaking wailing and crying of Gyutaro was a tear-jerker as he grew inconsolable.
At that time, Doma, the Upper moon one appeared in front of them, providing them with the remaining parts of a human body, asking them to turn into demons.
To save his sister, he agreed, turning her into a demon and both of them got merged into one body.
The bleak and ugly side of the society is realistically portrayed, as someone with no money, shelter, or food with unpleasant looks, they were outcasted by the people and were looked down on.
Such hostility from the human race had pushed them into the corners of grief that they could never fill, so instead, they turned against them, to devour them to their fill.
Sibling Hood In The Dark Side

An interesting contrast has been shown when Tanjiro fights alongside Nezuko to fight Daki, and their contrasting lives draw a very interesting parallel for the viewers.
Both the pairs have met with tragic consequences of life, but one chose the dark side to fight against humans, and another chose to fight for the humans no matter how much the dark side manipulates or overpowers them.
Given the animosity and hostility that Daki and Gyutaro faced, their lives have been validated by the viewers yet their acts have been unforgivable as killing people can never be justified by their tragic past.
It has been beautifully shown that in vulnerable times, any help humans get and they choose, defines their fate.
This unfair judgment can turn people’s lives against the mainstream moral consciousness that society operates.
Even in their lives after acquiring immortality, they have stood by each other, in their living as well as killing.
Their flashbacks and their bond were beautifully secured after they were defeated by Tanjiro, Tengen Uzui, Inosuke, and Zenitsu.
Despite all the hardships one faces in life, humans are bleak creatures of nature who cannot always differentiate between right and wrong unless it provides a solution to their condition.
It is not in their hands to dictate their fate but to change it and unlearn as well as learn what’s problematic and disturbing and how to make their lives better.
Through Daki and Gyutaro’s siblinghood and promise to stay alongside each other despite their appearances and differences, it is shown that even in the dark when fate chooses evil as a way, someone who sticks can make it a little bearable.