I Reincarnated as the Doomed Younger Sister of a Tragic-Novel Heroine

The Male Lead Thinks He Sees the Female Lead as a Little Sister, Then Realizes His True Feelings

Nothing too angsty!! The male lead doesn't have to reject the female lead when she confesses. It could be like Dada La Ai's "Sweetheart, So Clingy", or the male lead could genuinely see her as a little sister at first, then develop romantic feelings.

A Period Novel Where the Heroine Transmigrates Into the Original Heroine's Younger Sister

Any Book Transmigration Stories Where the Protagonist Becomes the Male or Female Lead's Sister?

Any novels where someone transmigrates into a book as the sister of the male or female lead? Ideally, she transmigrates as the villainess's younger sister or a supporting character's younger sister in an ancient-era sweet romance or a strong female lead story with secret identities! My standards aren't high: just make it good and funny!