Did a similar post earlier but I'm redoing it since my answers have changed. Including more demons, so these are my headcannons of what each demons scent is like and a little headcannon lore.
EDIT: I changed Akaza's scent because I had a better idea.
-Similar in a way to animals, demons each have a unique scent to distinguish themselves. The scents vary from demon to demon. Sometimes how they smell comes from who they were as a human before death, sometimes it just randomly creates itself after being turned, sometimes it forms due to the environment they live in or what they eat, etc.
-Demons will rub their scent all over their homes, their property, and their mates as well as around their hunting grounds to warn other demons that this is taken. They are very territorial and another demons' scent who isn't their mate will make protective and/or territorial urges arise to the surface.
-The stronger a demon is, the stronger their scent will be. However humans are not able to smell these scents (unless you're Tanjiro-) because their noses are not strong enough to smell them.
-A demon produces these scents naturally but it mostly seeps from their arms, hands, and upper bodies so the easiest way to rub their scent on something is to hold it or rub their arms on it. This is why family members who are turned together(such as Gyutaro and Daki) or demons who decide to be mates often scent each other by holding each other.
-DEMONS' SCENTS-
MUZAN: Tanjiro mentioned he smelled heavily of death and considering how heavy and dark the moons say his presence is, he probably smells VERY heavily of blood with a rotting body smell under it.
-UPPER MOONS-
KOKUSHIBO: Most would assume being the one who had received the most of their master's blood he would have a bad smell too, but surprisingly he has a very pleasant scent. He still smells heavily of blood being the strongest moon but he smells mostly like green tea and incense. Many female demons who had attempted to court upper one will often compliment on how nice he smells.
DOUMA: Douma and Akaza have similar scents since both have movesets based off winter, however both have different elements to distinguish them. Douma smells like freshly fallen snow, but freshly spilled women's blood and lotus blossoms as well. It's the biggest reason Akaza hates being touched by him.
AKAZA: Like Douma he also smells like freshly fallen snow but a heavy addition of gunpowder-smokiness like fireworks after they exploded.
HANTENGU/CLONES: The clones all have a different scent. Hantengu smells like an old dusty attic because of how much he hides in dark places, Sekido smells like the air after a rainstorm, Karaku smells a mix of sweat and surprisingly pine, Aizetsu smells like wet leaves, Urogi smells the most vile of the seven due to his hoarding/nesting issues but after he bathes, he smells like fresh hay. Zohakuten has the most pleasant scent of the seven being a mix of sandalwood and pine with an underlining smell of burning wood. Urami has the second best scent smelling like expensive tobacco and aged sake.
GYOKKO: Gyokko out of all the 12 Kizuki has the most unpleasant scent. He usually smells like sea salt and rotting fish, so other moons usually avoid him for this reason. Sometimes he'll have the scent of pottery clay and paint added to him.
NAKIME: Like Kokushibo she also has a nice scent. Some kind of incense with the distant hint of perfume underneath. After all she's still a refined lady even if she's a demon.
KAIGAKU: He has an ashy smell to him. Like how a burning log would smell after the fire dies down and the ashes are still smoldering a little bit.
GYUTARO AND DAKI: Tanjiro mentioned he smelt unpleasant and filthy, so I think he'd smell like rotting leaves/compost and blood. Daki being his sister has his scent rubbed off her but alone she smells like heavy perfumes and make up being an oiran.
-LOWER MOONS-
UBUME: Amarilliyas flowers. She used to plant them a lot as a human so it only makes sense she smells like the flowers she once loved.
HAIROU: Gunpowder with a heavy metallic tang to it. When he uses his wolf BDA the faint scent of wet dog can be smelled.
RUI: Rui has an almost clean untainted scent to him. He smells like freshly spilt blood in the fresh air after a rainstorm is over. It's as pleasant as it is dangerous.
MUKAGO: I think she'd have a sweetened-bad scent to her. Like a mochi cake that's starting to rot after going bad.
KAMANUE: I dunno why, but I think he'd smell like cotton. Maybe from the fabric he wears, or his softer features compared to the other lower moons.
ROKURO: Old milk and stale bread. I dunno why, he just screams like he'd smell like old food to me.
WAKURABA: Burnt paper. Yeah he doesn't get to have a pleasant smell either to match his unpleasant attitude in the movie.
KYOGAI: Old paper, ink, and leather due to his human self loving to write and his body being imbued with leather bellied drums.
ENMU: He smells a LOT like smoke and coal especially after he fused his main body to a train.
SUSAMARU: Cotten and rice because traditionally in the olden days, temari balls were made by stuffing rice into round cut pieces of fabric.
YAHABA: Soap and other various cleaning products they had around the Taisho period considering his germophobe personality.
-ALLIED DEMONS-
TAMAYO: This one's pretty easy. She smells like a lot of different flowers at once due to her blood demon art there's also an underlining medicinal smell to her too.
YUSHIRO: Yushiro has a heavy medicinal smell about him too considering he's around Tamayo alot. He masks his actual smell with his BDA to avoid getting caught so no one truly knows what he smells like.
NEZUKO: She has a very sweet smell to her like mochi cakes or sugarcane to match her sweet personality.
GENYA: Genya doesn't keep the smell after his transformation leaves but for a shortened time he smells of gunpowder. He also temporarily takes on the scent of the demon he eats. When he ate Aizetsu he temporarily smelt like wet leaves and gunpowder until his transformation wore off for example.
DEMON KING TANJIRO: Similar to Genya, Tanjiro only temporarily has the same heavy blood/rotting body scent as Muzan before he took overcomes his transformation.
I have a headcanon that kimegaku Susamaru hallucinated a whole sports anime backstory with Kanao (Todo style), to the point that Kanao is doubting her own memory bc of how sincere shes saying this
You guys went crazy over the last swap au designs so I give you more
Full hashira outfit designs because only half was shown + their weapons
The Hantengu brothers, living with grandpa Hantengu since Urami died and trying increasingly ridiculous stunts to kill peepaw and get that inheritance money.
Zohakuten, despite being the youngest, became a Hashira.
The new main trio. Unlike Tengen, Gyutaro is good at makeup
Music Mansion, the butterfly mansion’s counterpart + Enmu
(Make sure to count your shiny belongings before leaving, the triplets haven’t exactly unlearnt their thieving ways.)
Swordsmiths aren’t swapped so i can spread Gyokko/Hagenezuka propaganda
Prev. Frost hashira, the hand—not-exactly—demon
((i like minor background demons if you can’t tell))
Here's another random idea for a AU I had, let me know what you guys think of it!
Essentially, through unknown means, Nezuko is brought back in time, still a demon. However, she realizes all her abilities she acquired as a demon still remain, namely her immunity to sunlight! Not only that, she soon discovers another power: to convert other demons through her blood!
With new abilities at her disposal, Nezuko vows save as many humans as possible. Will she thwart Muzan's demon legion and create her own? Will the converted demons find redemption? Who knows...
