After Transmigrating Into a Book, Should I Choose My Master or Senior Brother?

Wen Niansu is in her early twenties, has cancer, and doesn't have long to live.

To survive, she is coaxed into accepting a mission to transmigrate into a book.

As a brainless cannon-fodder supporting female character, she has to keep mediating between her aloof master and her senior brother, who could turn demonic at any moment.

The mission seems simple enough, but!!!

Why are they looking at her like, “How could you do this to us”???

Her master smiles warmly. “Come here, my dear disciple.”

Her senior brother grits his teeth. “Junior Sister, come over to my side.”

Trembling Wen Niansu says, “No, I just want to finish my mission in peace.”