After Keeping a Yandere Villain Locked Up

[Updates follow the ranking schedule before signing, then daily after signing. Please add it to your favorites~] Blurb: Song Tang was born in a cultivation world on the brink of destruction. To save all living beings, she transmigrated into a storybook whose plot was about to fall apart. Her target, Fu Xuan, seemed on the surface to be a sweet, foolish boy who was half-deaf and half-mute. In secret, however, he was a ruthless, twisted schemer who would wipe out both the male and female leads. System: "Your mission is to: 1) stop Fu Xuan from killing the leads; 2) ensure Fu Xuan lives a long and peaceful life. Once you complete the mission, you'll receive one-tenth of this world's fortune, enough to keep the cultivation world alive." Song Tang nodded earnestly. "Got it, got it." So, on the night she transmigrated, Song Tang silently slipped into Prince Pingxi's estate, knocked Fu Xuan unconscious, and hid him in a mountain cave before dawn! Fu Xuan: ? System: ?? The storybook world's young Heavenly Dao: ??? No, that's too violent. We have to nerf her. "...Actually, there's another way to complete the mission. If you can change Fu Xuan for the better and reduce his world-destruction score to zero, you can finish early and return to the cultivation world. Would you consider it?" Song Tang pondered for a moment, then reluctantly said, "...Fine." And so: One month later, Fu Xuan murdered his father. One year later, Fu Xuan slaughtered his stepmother. System and the young Heavenly Dao: !!! What the hell do you mean, 'change him for the better'??? But three years later, Fu Xuan's world-destruction score really did drop to zero. By then, the male and female leads had taken the throne together after changing the dynasty. Fu Xuan had never spared them a glance, devoting himself instead to staying by Song Tang's side, washing her clothes, cooking for her, and joining her in punishing evil and promoting good. Aside from occasionally throwing a tantrum because he wanted her to give him a title, he had truly become a kind-hearted man who cared for the world, healed the sick and injured, and always wore a benevolent smile... The mission was a resounding success. Song Tang returned to the cultivation world without a hitch. But just one day after her return, the System forcibly dragged her back into the storybook: "Fu Xuan is going to kill the leads again! Hurry and stop him from destroying the world!" Song Tang: "???" The moment she appeared, Fu Xuan hurriedly tossed aside the knife in his hand and wiped the blood from his cheek. Then, looking innocent and aggrieved, he walked up to her with reddened eyes. "A-Tang, I wasn't disobeying you..." Song Tang glanced at the mountain of corpses and sea of blood behind him, fell silent for a moment, then nodded. "Mm, I know." How could he bear to destroy the world she'd saved with her own hands? This world must have bullied him again. A few things to note: 1. A slow-burn, long novel, 1v1 happy ending. Roughly half romance and half plot~ 2. The heroine returns to the cultivation world later on, and time passes at different rates in the two worlds: one day in the cultivation world equals one year in the storybook world. 3. Cultivation ranks in the immortal sects: Qi Refining, Foundation Establishment, Golden Core, Nascent Soul, Spirit Severing, Body Integration, Great Ascension, Tribulation Transcendence, Ascension. 4. A story built around an unusual idea, with lots of personal worldbuilding. More to come... Theme: Destruction and rebirth coexist