u/redhotphones

Her description BARELY matched him. In the manga her description of his personality was off, but the movie changes his behavior to better match (gentle, benevolent) so we’ll let that one go. But her physical description is off. "Blood poured over his head", the word used is "kaburu*"* which means to pour over the head, ie, pouring a water bucket over the head in the bath etc. If you consider the splotches on Douma’s upper body outfit you can SORT of see it, but the spot on his head is just too small for "kaburu". It’s absurd that Kanae found the time to describe the blood mark, but NOT his most striking feature — THE LARGE BRIGHT RAINBOW EYES. There’s literally NO excuse for this. Douma says he doesn’t hide being UM2, meaning he never changes his eyes.

"Weapons are sharp fans". THEY ARE NOT SHARP. We see closeups of them multiple times, and they are thick blunt metal slabs. Douma never ONCE cuts with them. In ALL cases he cuts with BDA and the fans are only for spreading blood, defense and bashing attacks.

Douma DID NOT REMEMBER the haori on first glance. He INSTANTLY finds Inosuke’s face familiar, but he needed to be promoted no search his memory to remember such a memorable haori from just 4 years ago? That’s not believable, CERTAINLY not when it was worn by someone like Kanae who stands out in every way. He canonically has very good memory. He DID seem to have known her at some level and it’s unclear what Kanae was doing meeting him while not in her haori — possibly Shinobu is correct and there WAS a relationship between Kanae and Douma, something which she couldn’t pursue as a Hashira.

If he got into a fight with Kanae there’s NO possibility of doing so without using his BDA. He can’t do cutting without his BDA so inflicting that wound is IMPOSSIBLE without his BDA. It’s completely beyond belief that Kanae, a Hashira even more talented than Shinobu, would fail to notice his BDA.

And finally, Dpuma WOULD NEVER LEAVE HER TO DIE ON THE STREET. She was downed, fatally wounded with her sword broken. There is NO explanation for Douma leaving her. If the sun was coming up he could simply CARRY her off. He would NOT lose the chance to eat her. Even if he felt she wasn’t worth eating, he’d at LEAST finish her off, not leave her to bleed out. It’s not in his character AT ALL.

So what’s the explanation? The manga only shows a 1st-person perspective of Kanae attacking then blood flying out of her head, but the anime shows Douma apparently slashing her her breaking her sword at the same time. Besides the fact he couldn’t break anyone else’s swords, this was shot in a dream-like way with no background and flying petals. He INHERITED that memory from a different demon he absorbed.

Because it was an absorbed memory he didn’t have instant recall, and it’s more of a dream to him. The reason why she didn’t mention the BDA was because the sharp fans WAS the BDA. The best match I’ve found is the demon in the Flower Breathing Hell interview. Gentle and smiling, fan marks on his/her face, and the hair is long and dark so it’s possible it could have a blood-poured-over look. Scholar thought they were Koku’s student and I was meaning to research that possibility.

Databook only says he "broke" her ("yaburai"), NOT killed. Broken is never used to mean killed / defeated in the databooks. Douma himself NEVER admits to fighting her or ANY Hashira for that matter. He canonically is rarely sent on missions, it would be very strange for him to show up at some village street randomly, just for a fight? Nonsense.

It wasn’t Douma.

There's no direct evidence, but there are too many links and parallels between Sister, Shinobu and Douma. I think it's likely that Spider Sister is in fact one of Shinobu's tsuguko she thought had died.

Appearance. Demons change features, in particular the eyes will usually change shape except for prime demons (the four "cats": Muzan, Nezuko, Tamayo and Yushiuro). Unfortunately, Sister's original form is very blank-looking. Her hair doesn't match the style of the tsugukos in Shinobu's defeat flashback, ie, Sister's bangs are tied up. However, there could be a reason for hairstyle change....

Link to Douma. Shinobu says "according to information from our sister" when talking about Douma, who is she talking about? NOT Kanae because Shinobu directly rejects Kanao from that relation in the SAME discussion ("I'll talk about the demon who killed MY elder sister"). She absolutely would not change her tune in the middle of the same discussion. Shinobu canonically treats all the girls of the Butterfly Mansion to be her sister. Besides, she would just say "Kanae" if that's who she meant. I used to think it was Aoi because of narrative reasons but there's NO hint that Aoi was ever away from the Mansion. So it has to be one of her other tsuguko.

How? By infiltrating Douma's temple.

But Douma is a white birch, a divine spirit clan. He can (probably) read minds and sees the lines of fate and karma, there's no way someone who isn't prepared to deal with an angel person is going to get away unnoticed. So Douma caught her.

But is it guaranteed that Douma ate her? What if she begged him to be turned into a demon instead? What if Douam read her karmic fate and offered her his blood? Ie, "you can live in peace within me, or you can take some blood, although you will have a pitiful end". She took the blood....and ended up losing her memories as demons often do.

Too weak to behead demons. At first, Sister didn't understand why Shinobu didn't behead her. But then she thinks "I see, she's too small and can't decapitate demons!" That's a VERY strange conclusion to make on the spot. Shinobu just effortlessly dominated her, a demon, physically. Does she have experience with Slayers not being strong enough? She in fact has zero combat experience, and all she does is run away even from fodder Slayers. She calls for Father to help instead of fighting. When faced with Murata, instead of attacking him she wraps him in the binding web.

Maybe she's TOO WEAK to tear apart a human. She CAN'T physically kill a human, CAN'T tear them up to eat them directly so needs to use the binding web acidic cocoons. She talks about how the clothes "getting in the way" will be melted and then she will feast on his liquefied remains......what? Why doesn't she just kill and eat him on the spot why go through all this just to kill and eat one fodder? Why? She's TOO WEAK.

She THINKS she's too weak.

Why does she think that? For the SAME REASON she thought SHINOBU was too weak to behead her. Someone TAUGHT HER to think this way.

SHINOBU.

It was SHINOBU who told her, as a tsuguko, that she was TOO WEAK to behead demons. She's too small and doesn't have enough muscles. But that's not a problem, even if she can't behead demons she can still help. She can still contribute. BY DOING INFORMATION GATHERING. Hence, going to Douma's temple. She was smart, careful and serious, she can definitely do it. So she went.

Douma and Rui's mountain. Douma DIRECTLY mentions "Rui-kun's mountain" in his fight with Shinobu. He says her poison was much stronger than what she used there. That means he can JUDGE the strength difference. He's experienced the effects of what she used on Rui's mountain. How? Maybe someone gave him a sample, but I tend to doubt it. Shinobu would NEVER let Kanao anywhere near her poisons, although I'll admit it's not impossible (ie, maybe this was the reason for Zenitsu taking the fish tank out of Shinobu's room, ie, Kanao used the other girls as proxies to get Zentsiu to get it). So how?

He felt it....via Spider Sister. He was monitoring the battle via blood comms with her. I'm not sure blood comms is THAT strong, at least not from a very far distance. Maybe that's why, though, he suddenly seemed to know who she was the moment she hits him with the poison.

Because, if he recruited Spider Sister, she becomes HIS responsibility just as Kaigaku became Koku's responsibility. She would have become Douma's subordinate. He may have sent her to Rui mountain which is why someone who clearly comes from an urban setting was running around in the middle of a mountain being chased by Slayers. She was Douma's woman on in the inside of Rui's family.

Now consider, I proven already that Shinobu was research partners with Spider Brother who is also the true LM5. Maybe just as Shinobu sent a tsuguko to infiltrate Douma's operation, Douma sent that same tsuguko to infiltrate Shinobu's operation.

Settling Shinobu's karma. Shinobu had no idea that Sister was her tsuguko who had lost her memories and who had transformed her appearance. Shinobu crushed the Sister with power, and so, Douma crushed Shinobu with power. But he didn't pay back her karma for all the demons she's killed, ONLY for Sister. Does he just magically know how she's killed all those demons? No, but he DOES know how she killed SISTER.

And so the tragedy of the nameless tsuguko concludes. I wonder if Shinobu saw the truth when she was in Douma's soul network? The chapter's cover in which she fights Sister (chapter 41) shows her treading the water of Douma's lotus garden.