I watched the first episode of The Apothecary Diaries, and the opening is very reminiscent of a different and much older anime: The 1984 Glass Mask TV series.
Here is that intro:
And here is Glass Mask:
Between the heavy focus on the main heroines, the black background, and even the head movements, I can’t help but see similarities between protagonists Maomao and Kitajima Maya, respectively.
It might just be a coincidence that they’re similar, but I’d love to know if any inspiration was taken.