Novel's Extra: I Awakened The Strongest Physique From The Start - Chapter 138 - 137 - Magic Circle.

Chen Minhao found himself transmigrated to a parallel world in China, and he even became an idol trainee. By virtue of his efforts in mastering his IQ, EQ, and his looks as his weapons, he became a celebrity with a huge fan base step by step, and ultimately became a global superstar that conquered the both the fields of acting and singing.

- Description from Novelupdates

Upon meeting the girl who would become her adopted younger sister, the duke’s daughter Christina regained memories of her previous life. Through those memories, she learned that her new sister, Mishuli, was the heroine of a certain story. And though the story depicted a Christina who abused her sister, the real Christina turned into a siscon who spoiled Mishuli to no end.

“Jiang Yu transmigrates into a novel and becomes a side character in the book.