Mage Manual - Chapter 23 - Observer? Sword Maiden?

No matter how twisted the world becomes, humans will always remain humans.In the face of their doom edging closer, their greed doubles instead of fading away. Their selfishness is unwavering—they simply want everything, even at the cost of endangering those closest to them.For that is the truth of humanity.So, if everything is linked to iniquities and sins, then unlike them, I won’t shy away from these possibilities—I will embrace them.---Synopsis:Kael, a young man from Earth—a dimension renowned for its technological advancements and brilliant minds—returns on a tour sponsored by his school.But fate has other plans.A Dimensional wave crashes into Earth, mutating the entire world into a grotesque landscape of unexplored horrors.Those who survived the dimensional impact awakened to newfound strengths, while those who didn’t perished—or worse—transformed into monstrosities far more fearsome than any beast.The world has returned to the law of the food chain. The strong will endure and rule, while the weak are devoured.Kael must cling to his sanity and navigate this nightmarish new world with a mission: to protect all he has left.But things take a darker turn when the system he acquired reveals an unexpected and horrifying backlash:{Consume human flesh}{Or perish within the next 24 hours}The clock is ticking, and Kael is left to grapple with an impossible choice that could seal his fate—or his humanity.

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

Doomsday crisis, zombies are attacking, the situation is critical.Don't let our enemies change from zombies coming at us to humans we protect behind us.“Brother, what would you do if I turned into an irredeemable zombie?”“…kill you.”“Then do you know what I would do if you turned into a zombie?”“Kill me.”“No,” he lifted her long hair, revealing her smooth neck.“You are crazy. I advise you to give up this irrational idea.”“Brother, this world has gone crazy.”

The scum’s or villain’s long road of transformation was tentatively set to the world:
The abandonment of the educated youth’s wife (Completed)
The hidden marriage of the scum film emperor (Completed)
The best brother in the world (Completed)
The Phoenix male who destroy the bridge after crossing the river (Completed)
The treasonous general (Completed)
I’m an honest man (Completed)
To become the top scorer in the School of Agriculture (Completed)
The soft rice man’s self-cultivation (Completed)
The whole world is reborn (Completed)
I want to survive on a desert island (Completed)
The stallion male who has seized the opportunity (Completed)
The perverted self-salvation (Completed)
The spring of the loafer (Completed)
The misplaced life (Completed)
The miser career (Completed)
The ghost is out of feeling (Completed)
The Queen’s favorite husband (Completed)
The vicious girl with her godfather (Completed)
I want to be a good person (Completed)
I does not tear up the family (Completed)
The perverted common plant (Completed)
The Mary Sue’s men (Completed)
Every time I was reborn, someone wants to kill me (Completed)
The old people’s counterattack path (Completed)
The global evolution (Completed)
When I became a net red (Completed)
For you, good person (Completed)
His heart had white moonlight (Completed)

- Description from Novelupdates