Toaru Majutsu no Index - Volume 7, Prologue: Begin Action. The_Page_is_Opened.

Ashley Gusman, a determined young Filipina, was driven by her sole ambition to provide a better life for her family. She was willing to go to great lengths to achieve this goal, even taking on the role of a surrogate mother for a Billionaire Heir.***~***CEO Tanaga Jones, who needed an heir for his empire, was adamant about not wanting a wife. Ultimately, he contracted with a woman to bear him a child.

Su Ran, a music prodigy, woke up transmigrated into a book.

At that point in time, the main story arc in the book had already been completed. As a villainess female supporting character, not only did she need to take over the original owner’s pitiful life in poverty, she also gained an instant son right at his rebellious period.

Ten or so more years from then, the son would turn into a twisted, evil villain. He would appear in one of the extra chapters to pick on the male and female lead’s children.

***

Su Ran: Son, you shouldn’t be too outstanding.
Su Han: Why not?
Su Ran: ’cause you will be killed.

Su Ran: Son, would you like to learn music from me and become a zen, little fairy boy who only needs to drink dew.
Su Han: No, I want to go into business so I can support you.

- Description from Novelupdates

Ning Yechen used to be the Demon Lord. He singlehandedly took over the Demon Realm and attacked the Heavenly Realm. His name preceded him throughout the Six Realms. He got tired of fighting, so he quietly went into seclusion and became a happy hermit.One night, an Empress from the Heavenly Realm fell into the Mortal Realm after someone drugged her with an aphrodisiac. She inadvertently fell into his room, and they made out. After the deed, the Empress quietly left. Just when he thought he would never see her again, she showed up in front of him ten years later, bringing a child, saying it was his daughter and demanding accountability from him! “She’s your daughter. You have to be responsible for us!” Ning Yechen was stunned!

【Welcome to the Love Simulator】【You can freely choose to simulate with women whose appearance rating is 7 or above (on a 10-point scale) and have basic connections to your reality.】【The simulation is entirely free; please explore on your own.】【After the simulation ends, the system will evaluate the results and provide rewards.】【Current number of simulations: 4】【The number of simulations is not fixed and can be restored through special rewards or the passage of time.】Wait—why are all the simulation targets such difficult-to-handle 2D female leads?