Being the Female Lead's 'Brother' Isn't Easy (Transmigrate into a Book)

This novel is officially complete. Please do not repost it. My next historical novel, "Young Master, Help Me (Transmigrated Into a Book)," is almost complete.

An ambitious little maid who loves to secretly stir up trouble X a cunning, fiercely protective minister with a strong possessive streak

Blurb:

What do you do when you transmigrate as the female lead's fake "older brother"?

After playing a raising game to its bad ending, Bai Yu'an, a devoted player who had spent real money on the game, furiously complained to the production team. She was rewarded with access to the game's sweet, angst-free route and transmigrated as the female lead's twin sister.

To protect her family, Bai Yu'an disguises herself as a man and vows to become the family's pillar!

Our goal: Protect the female lead and find her a good husband!

Shen Yi confesses earnestly: "I promise that your younger sister will have a smooth and peaceful life from now on."

Bai Yu'an nods in satisfaction: "Good. You're the one!"

Shen Yi: "I mean, as long as you obediently stay by my side, you won't have to worry about your sister anymore."

Bai Yu'an: "..."

Can someone explain why the brother-in-law she carefully picked for her sister talks so strangely? And what's with her sister's smug, 'I'm selling my sister' grin?

P.S. The female lead disguises herself as a man and has a fiery temper. The male lead is jealous and a little scheming. If you dislike the characters, please click the X. If you drop the story, don't tell me.

Theme: Protect the female lead