I Cross Over for the Sickly-Sweet

I'll think some more about the title and blurb. Both will need changing before I start writing. The newly risen demon lord of the Demon Realm was once human, but fell into demonic corruption. His baleful aura blotted out the sky. A monster through and through, he plunged the Three Realms into rivers of blood and chaos, leaving them in turmoil. The Star Lord Tianyuan cast a divination. To end this calamity, Shaofuxing of the Star Palace had to descend to the mortal realm. Shen Shaofu, who had only ascended to immortality a few centuries ago, was utterly bewildered. Star Lord Tianyuan patted her on the shoulder. “Either kill him or redeem him. If you succeed, you'll gain a thousand years of cultivation.” Shen Shaofu: “...???” Star Lord Tianyuan: “A thousand years! Think about it! Worst case, you die and your soul is destroyed. I'll fish you out of the cycle of reincarnation, and in a hundred years you'll be a fine immortal again.” Shen Shaofu: “...” In the end, Shen Shaofu had no choice but to descend to the mortal realm and face her trial in the Demon Realm. When she finally laid eyes on the legendary demon lord, a cold-blooded killer of demons, as beautiful as a flower, for one fleeting moment, Shen Shaofu thought he looked so pitiful. Like a dying madman, a lone wild goose with broken wings. Even his soul was wailing. But the demon lord suddenly smiled tenderly, as if he had waited a long time for this moment. He spread his fingers “Caught you.” In an instant, blood surged like a waterfall. A forbidden spell was unleashed, the stars shifted, and the seas and fields transformed. She had returned to several centuries earlier, before Shen Shaofu had ascended to immortality, when she was still a junior sister in a cultivation sect. And the demon lord was still a boy from the foot of the mountain, abandoned in the wilderness, without parents, bullied by others, yet still with clear eyes. Since she was here, she might as well make the best of it. Shen Shaofu, already a fully graduated immortal with maxed-out cultivation, had no choice but to start all over again. She might as well take him in and see if she could redeem him ahead of time. If she could get him to be more positive and sunny and keep him from falling into demonic corruption, that would count as good karma. But Shen Shaofu had forgotten that they had met long ago. She also had no idea that his clear eyes were an act, that he was pretending to be bullied, and that Pei Xingluo had known who he was all along. He gave everything he had, just hoping that star would fall beside him once more. A little scene I wrote on a whim: The red-clad boy, his collar, face, and hair dripping with blood, gently smiled as he stroked her face. His fingertips held the warmth of spring. Yet stained with blood, they were a horrifying sight. “Why are you trembling?” “Oh...” Pei Xingluo spoke to himself, lowered his head, and looked at the blood on his clothes. Malice churned in the depths of his eyes, but then he said anxiously, “That isn't mine. He wanted to hurt you. He deserved to die. Don't be afraid.” Shen Shaofu held him tight. “I'm not afraid.” Even if she were reduced to ashes, she would fall with him. Note: You may not believe it, but this is a sweet romance. (The title and blurb may change. I'll try to keep the tone light, but the author's desire to write a yandere male lead remains unchanged., 2021.8) Theme: Love is truly great.