theorizing abt beast kyoka
(repost again, but this one is more high quality)
so firstly, she's dressed so similarly to how koyo dresses, she has that mantle, the obi sash, the hair pins on either sides of her head, etc.
now I'd love to consider how there is no mention of koyo in beast (manga), kyoka herself doesn't have much character but hear me out what if koyo managed to get herself out of the mafia? that's why kyoka's clothes are similar to hers, be she's taking the place that was reserved for her.
They are paralleling too, in og!bsd, koyo gets captured by the ada but in beast it's kyoka, in og!bsd koyo's admirer gets killed but in beast atsushi gets into the orphanage w mori and also kyoka (since dazai told him to retire alongside kyoka), he did what koyo and her admirer couldn't, which proves that kyoka is in koyo's place here, reminder that koyo was only 14 when she tried to escape, beast kyoka herself was only 12.
So like mentioned, she wears a mantle like koyo but one thing that differentiates is that koyo has blood splatter/tree branch like design on the end of her mantle whilst kyoka has hers tainted with black; her background is probs similar to og!kyoka, her parents were killed, she got into the mafia and all, so I think that her mantle is stained bc in the og! bsd, koyo gives kyoka the documents that show that her parents murder wasn't her fault but in beast we don't have koyo so there's no one to prove to her that she isn't at fault, so the mantle is soaked w blood be she believes that she's the cause of her parents' death.
in og au, kyoka has sprouts on her kimono to show her growing nature but in beast, kyoka has merely some squiggly lines (showing the flow of wind) and a few small florals/bits of snow on hers which resonates two things: 1. if those are bits of snow it can be be of demon snow, it's the symbolism that she thinks her ability, demon snow is the cause of her parents death. (like I said earlier) 2. if those are small flowers it is to show us that she is like them flowing into the direction life leads her to and adapting into it no matter what.
also, abt koyo, in og bsd she's close to mori but in beast, mori is an orphanage director while dazai takes his place, n atsushi is close to dazai, kyoka is close to atsushi therefore kyoka's in koyo's place technically as koyo must've escaped the pm the way ango betrayed them (somewhat similarly.). it's like chuuya-koyo-mori trio but in beast.