Probably something started by Kawashina then followed by other Shibafu-fanartists like Matsutani. Sometimes this kind kind of stuff just happens out of nowhere, like 'Battle Axe Shikinami' from last year.
Hatsuyuki being the strongest is always a theory I have about her, as she has this aura of being a wild card about her. Also, no Murakumo? For shame, I get it that its only Shibafu's designs, but come on, you can't keep the best one out.
• A devil who lifts up her skirt
• Thick (not telling you where)
• Let's draw her navel in the hope of breaking through the event sea areas• Big-hearted, even though she's the eldest child
• She has a way of saying "I think that'd be nice though"
• If she becomes serious, it'd be an ending where she goes MIA, like AmuroFubukiShirayukiHatsuyukiMiyukiIsonamiUranami• The mediator between the sisters
• Hard-worker and possibly a worrywart
• If I'm going to draw a lewd book, it must be her.• Strongest among the sisters
• High level of seriousness
• A heroine in peril• Among the sisters, she's bad at self-assertion
• Seems like her actions would backfire
• She could muster up courage when situation demands• Good sense of judgement and caring
• The linking bridge with citizens
• The architect of death flags
