Toaru Majutsu no Index: New Testament - Volume 17, Chapter 3: Or Isolation Surpasses a Group - Engage_U.F.O.

Immediately after Gu Changge realized he had transgressed into a fantasy world, the world’s protagonist, and fortune’s chosen, vowed to take revenge on him. Envied by all, he not only has the female lead head over heels for him but he’s also treated as a distinguished guest wherever he goes. Fortunately, Gu Changge’s prestige and power are superior to everyone else’s, so shouldn’t it be easy to trample on a mere fortune’s chosen?

Li Hua's reign as the twenty-first century's deadliest assassin ended in fire and betrayal. Her own sister, Li Min, turned their elite force against her, leaving nothing but ashes where a legend once stood.In the moment of her death, Li Hua's soul tore free from its earthly bonds, hurtling across the boundaries between worlds until it anchored itself in a new vessel in a realm of ancient martial arts and mystical cultivation. Through this impossible transition, her inner space remained intact—and with it, Little Firefly, her spirit companion.Here, where qi flows like rivers and mountains bow to those who master their cultivation, Li Hua will forge herself anew. No longer content to be merely an assassin of mortal flesh, she sets her sights on ascending to immortality itself—a journey that will shake the very foundations of heaven.

Content Warning: R-18, Smut, Cruel MC[Ding! You've acquired the Heroine Stealing System!][Your first task is to steal the daughter of the Eastern Kingdom's king!][Your Fate Value has increased by 10!][You've slept with the hero's mother, your Fate Value has increased by 15!][The hero has developed animosity towards you. Current Hatred Level: 5 stars][The king's wife is charmed by your looks.]After being transported from his own world, the protagonist wakes up as Vritra, the son of Demon King Rohan from the Hell Continent.Since he's from another world, he doesn't have any Fate Value in this new world of swords and magic.To survive, he has to act like a villain, stealing the affection of every hero's heroine and sleeping with them.This will boost his Fate Value and help him stay alive in a world filled with wars and political conflicts!

There was a Senior Brother and a Junior Sister. One of them was transmigrated to this world and had cheats while the other was the reincarnation of a Great Emperor.