From Human to Skeleton: Revived with Infinite System Crystals - Chapter 4: The Demon King’s Daughter

Arren was reincarnated as an extra in the book world. However, unlike the others, Arren was determined to play his role well and be the best extra ever.He was successful until that one unfortunate night that would make his second life an unpredictable one. He also began to doubt that perhaps... He wasn't the useless extra he always thought he was.R18.OMEGAVERSE/ BL

1. Download a suspicious game
2. Catch a few magical pets as partners
3. Go through interesting daily routines and lead the pet shop to a whole new level

- Description from Novelupdates

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.

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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

Lin Yi failed the college entrance exams and chose a diploma mill university.

And as deserving of a diploma mill university, the first line of the admission letter read:

- Description from Novelupdates