I always wish this story will have Morgan le fay children, Finally my wish is finally come true, Fujimaru Calisto daughter of Fujimaru Ritsuka and Morgan le fay.
It's not tagged at the source at all but I am 99% certain this is an original alternate design of Aoki Lapis based on the hairstyle and scarf. The artist also seems to really like Lapis.
So the artist made a second one 2 months after the first one with a few things "corrected" https://twitter.com/nantara3080/status/1785230467777847644 so I'm posting this here in hoped of someone translating the new tidbits that were added.