The Mood of the Possessed Novel is in Crisis

Summary

I've been reincarnated into a novel written by my late sister. But something is wrong... the world I've entered feels strangely off. My sister's good karma earned her a final wish, and I, her younger sibling, am chosen to fulfill it. My wish is to live as her most beloved character. The problem? I've become the villain, Satin, and the righteous protagonist, the holy knight Cain, just won't leave me alone. "Don't give me that disgusting look." "Satin, get lost. Just die." He was a brat... a prickly little kitten, even as a child?! As I dig into the novel's hidden secrets, an incident brings me and Cain unexpectedly close... "Satin, I thought you were gone. So I was going to... murder them all!" Murder them all? This guy is completely insane...