After I Transmigrate into a Book, I Strive to Become the Demon Lord's White Moonlight

Chen Xiaoxian, a famously dim-witted player, transmigrates into a book. She remembers that she is supposed to become the male lead's beloved, white-moonlight girl, steal away the gentle and lovely senior sister, take the hot and gorgeous little witch with her, and make herself the only one in the male lead's heart: Chen Xiaoxian!

But can someone explain why, even though she's been working hard to help the male lead, who's undercover in the Demon Palace, complete his missions, he still can't feel her love?