The description translated into English:
“Charlotte, a bookworm who dreams of becoming a writer, begins her new job as a servant to Mr. Matthew and his sister Anna, the last remaining members of the Parvens family. Her writing skills attract the attention of both. Now, for Matthew, she is tasked with writing letters posing as him, while for Anna, she must secretly report on Matthew's daily affairs. Putting pen on paper has never been so difficult! What will become of Charlotte when the Parvens family's twisted deceptions come to light?”
(I used Google Translate, so the translation may not be accurate)