My Junior Sister Really Isn't the Villain

Updated whenever I can, with only a rough outline. [Flirtatious, naturally absent-minded, occasionally goes dark, junior healer] [Upright on the surface, truly righteous, cool and caring big brother, master of all sorts of cultivation] Only after Ni Shu fell into the water did she learn that she was living in a world where two "reborn stories" overlapped, and that she had become a target for the protagonists to assassinate. But because the transmigration System had malfunctioned, she could never win over either protagonist. With her attempts to stay alive failing, Ni Shu had no choice but to cling to another powerful ally: Shen Ju'an, the senior disciple of Lianfang Peak next door. He had countless secret identities, powerful connections, and was currently an underdeveloped mother-hen. Shen Ju'an was assigned to look after a little girl, supposedly an unwanted junior disciple from Feiyun Peak next door. He'd intended to refuse, but it was hard to disobey his master. His master smiled with gentle, unsettling warmth. "She's a good girl who won't cause you any trouble. You don't need to feel too burdened." But... the little girl was truly gifted... One month after taking her in, his junior sister blew up the alchemy furnace. He hurriedly carried the soot-covered child to the river to bathe her. Two months after taking her in, she set her room on fire and burned off her eyebrows and hair. He rushed to put out the flames in the middle of the night, then spent the rest of the night by lamplight helping her grow her hair back and style it. Six months after taking her in, the little girl lost control of the crane fire in her hands while making a puppet and burned all her clothes off. He charged into the flames with his eyes closed and carried her out. They both smelled like roasted meat. And then... as he watched the fire flare up again, Shen Ju'an could take no more. After a long pause, he said seriously: "Junior Sister, use me for your experiments from now on." If she burned him to death, he wouldn't have to face this terrifying world anymore. But how could Ni Shu hurt the powerful ally keeping her alive? She quickly settled Shen Ju'an somewhere safe and said with utmost seriousness: "Senior Brother, you're my life. You can't get hurt." Shen Ju'an: "…" Later, the immortal sects of the Nine Provinces joined forces to hunt down Ni Shu, the Nightmare Demon. But no one could suppress the Nightmare Demon's crane fire in her hands. Only Shen Ju'an charged alone into the Dao Seal barrier, holding up the sky for her as he reasoned with her: "Shushu, be good. No more playing with fire. You'll hurt me." [Reading Guide] 1. The script is incomplete, and this is not a typical story with multiple reborn characters. The heroine is not a villain, and the truth won't be revealed until later. 2. The setting is the Age of Declining Magic, with my own take on cultivation. The stages are: Qi Refining, Foundation Establishment, Golden Core, Nascent Soul, Cave Heaven, Bright Platform, Deification, and Ascension. 3. A lighthearted story about mutual devotion and healing. 4. Happy ending. Blurb revised on 2023.4.7 and saved. Theme: My fate is mine to control, not Heaven's