The parent post's source is tagged Rem in pixiv, and the links are predominately to Rem themed doujins in the artist commentary. While she has long hair, her bangs and the hair framing her face are the same as Rem with short hair and she's wearing the same hair accessories as Rem (the X hairclip/ribbon and flower knot). Not sure what other features you want the artist to include for a nude character that would identify her as the character they say she is.
