After I Transmigrated into a Book, I Got a Happy Ending with a Nonhuman Villain

One-sentence summary:

After awakening, the heroine discovers that she has transmigrated into a book as the tragic white-moonlight character destined to die. To survive, she makes a happy ending with an inhuman villain.

A gloomy tentacled sea god from the deep sea vs. a little witch who will have her blood drained and heart carved out in the future, but is now focused on staying alive.

Theme: Bravely pursue freedom