[Transmigration + cultivation + System + misunderstanding-fueled overinterpretation + mutual devotion + hilarious power fantasy]
Su Qingran transmigrates into a cultivation novel as a good-for-nothing, gets framed and thrown into the Pit of Ten Thousand Snakes, and is about to meet her end when her late-arriving golden finger finally comes online:
[The Suffer to Become a God System]: Take the nastiest beatings and gain the biggest cultivation boosts!
Snake venom +100, gale-force winds +100, lightning strike +1000... The more she gets beaten, the prettier and stronger she becomes, coasting all the way to ascension.
But her aloof senior brother, Mo Yuan, has gone mad:
He is actually a reincarnated Demon Lord bound to the “Ultimate Villain System,” whose mission is to torment Su Qingran until she is disgraced and ruined.
And yet...
He shoves her into the snake pit, but she drains the venom from all ten thousand snakes overnight, then clings to his leg and cries, “Senior Brother, I understand how much thought you put into this!”
He opens the Gale Chamber to break her will, but she finds the wind too weak and pounds on the window, shouting, “Senior Brother, did you skip dinner? Turn it up!”
He publicly accuses her of turning demonic, but she becomes both god and demon, makes her debut center stage, and is still moved to say, “Senior Brother, you’re protecting me again!”
Mo Yuan: ...System, please, make her act normal!
Later,
He betrays his sect for her, fights his way through the divine realm for her, and burns his demon soul for her;
She withstands heavenly tribulations for him, devours the System for him, and remakes the Three Realms for him.
All living beings think they are gods and demons locked in opposition,
But they do not know...
She is the one exception in his life,
And he is her greatest cheat.
“Senior Brother, what if you’re the villain again in the next world?”
“Then I’ll keep saving you until you become a god, until I become the villain who belongs to you alone.”