It’s mainly because of the hair and outfit. This is one of the fairies in the manhwa “Follow the Breadcrumbs” that appears in the latest chapter.
This is Juvia from Fairy Tail.
I thought of Juvia when I first saw her for some reason even though last time I watched the anime was several years ago.
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I think there's a word to describe when you've seen things and it reminded you of it as a nostalgia but then you somehow think to recreate their appearance as an original of their design when you've only little bit vividly remember what they've looked like. Example is Pikachu's tail, u might wanna search for it. The author must've accidentally had that vision as she's most likely have probably seen Fairy Tale Juvia.