I Am The Last Villainess He Has To Kill summary:

When people get transported into novels, they usually end up as noble ladies, even if they're villains. But I ended up as the final monster that the male lead must kill—the daughter of the Demon King."Here’s your favorite finger necklace, Princess!"Abduction and murder are the norm among demons. I can’t live with these creatures for 5,000 years! I just need to endure it, fulfill my role according to the original story, and move on to the next novel! Oh, God. How is this even possible? This isn’t some stray cat adoption; it’s like adopting the male lead! And the eight-year-old Kiel is saying some very ominous things.“Can I eat you?”"Well... I’ll raise you with care, so come kill the Demon King’s daughter later."