Today I want to talk about Mutsuki and her hair. Mutsuki has straight silver hair that, when left natural, goes to her ankles, but I'm admittedly not confident on this. It's honestly difficult to say just how long her hair exactly is: Her base sprite has her hair posed in such a way that it's tricky to tell, but almost definitely goes down to at least her calves. There's exactly one cutscene that also shows her base outfit's hair that isn't cut off by the screen, and that also seems to put her hair at calf-length. The anime seems to agree that her hair would go down to her boots if not being blown by the wind, which would, at the height it's tied, bring her hair to ankle-length. Mahjong Soul has her bond style, which does have her hair close to natural, and it puts it to her calves, as does the qipao (though I'll go over them in more detail later). There's also Fankit 54 which shows her hair being straightened, and seems to place it about knee-length. All this is to say that first, take this length with a grain of salt. Second, however, is that I'm going to claim that Mutsuki does this intentionally, tying her hair or using other methods to obscure her actual hair length because it's an easy prank that's simple to do, and it never gets old to watch someone react with incredible shock when her hair seems way shorter than it would otherwise be. But I digress, I've gotten ahead of myself. Mutsuki ties her hair with a black flower hairband that's as big as her head, with a maroon inside that matches the clothes she wears, as well as her thorny halo. Her hair is tied up on her left into two sidetails, likely to help her use her gun better (and possibly hide a trick on her left, rather literally being sinister with it). The smaller sidetail is a messier sprout, curving straight back at her, with a bit of it going up instead of down, also curving straight back at her. Her bangs are mainly on her right, what would be on the left being in her hairband. Said right bangs go down to her chest. Outside of that, she has a strand of hair that goes over her ear despite looking like it would naturally prefer to not do that.
Mutsuki's New Year outfit has her tying her hair up in three buns. The biggest one is the one that's slightly to her right when accounting for her head tilt, the second biggest one being right behind the front one (and is essentially hidden outside of certain angles on account of her halo perfectly being in the way). This is also where her ponytail originates, curving to the left in her chibi, likely because of how much she wears her hair in a left tilt that her hair got used to that being the natural order of things. Finally, between the two hairbuns in height and to the right of both of them in a way that forms a triangle, is the smallest one of the three. Mutsuki wears what might be a cherry blossom wreath. I say might be, because her sprite suggests such, but her chibi contradicts that, but that's likely because part of the wreath goes into the hairbuns I talked about earlier, meaning it wouldn't make sense to model that. If it's not a wreath, it certainly seems crown-like at least, which feels like a very festive way to celebrate the new year.
Mutsuki's dress outfit has her hair in curls, but it's also incredibly difficult to tell how long her hair is because of the puffy article she wears as well as the frilly dress (and lack of a chibi). If I had to guess, with the curls she has going on, it goes down to her thighs when she's not wearing the fur, probably her upper thighs? Besides that, her hair now has a sidetail on her right, likely coming from the hairband she's wearing, as that top part to it seems to be where it's originating. That "top part" might just be her flower ornament, though it seems a bit too small for that to be the case. Her bangs are also in a more natural position, showing how they typically fall, and they fall in an impressively straight pattern.
Mutsuki's undercover outfit is a dapper suit that shows what I meant by Mutsuki's hair being wildly inconsistent, because it only goes down to her thighs! However, it's plausible that this is because Mutsuki's hair was previously curled, and this is just her hair being tied together to try and sell her disguise a bit better. This would also solve the mystery of what's in her dress outfit's hair: It's the same thing she's using to tie her hair together in her suit. She's also tied her hair lower, likely to avoid raising too much suspicion (and to make it harder to determine who she is when she's not wearing this, to keep some heat off her and PS68's back). It's a nice outfit, but I prefer the dress more.