Chuan Shuhou Wo Lian Nü Pei Dou Bushi

After her college entrance exams, Su Yao's sister frantically recommended a smutty novel called [Coincidentally, I Like You Too.] Driven by a noble pursuit of knowledge, a desire to explore the unknown, and a thirst for academic innovation, Su Yao decided to peruse this work one dark and stormy night. The result? She transmigrated directly into the book.

She became a nameless, faceless background character—and thank god for that! If she had been anyone with even a remote connection to the plot, she would have died from pure disgust. After all, who in their right mind would want a starring role in a smut fic?!

Her new rules for survival: The Male Lead? Stay far, far away. The Female Lead? Never, ever offend her. A fellow Background Character? Now that's a safe bet. And so, Su Yao—now living as Lin Zhinian—confidently befriends another "background character," Shen An.
Everything is going perfectly until the day she personally hears the novel's original male lead call Shen An...
"Brother"

(Source: Bilibili Comics, translated)