The Salted Fish Senior Sister is the Villain's Dark Moonlight

Jiang He transmigrated into a novel—but arrived fashionably late, missing every plot-altering opportunity. No problem! She'd just lay low as a nameless extra and enjoy the cultivation life. After a peaceful hundred years of lazy training, a glitchy system rudely flings her back in time, forcing her to become the male lead Shen Xingyun's golden finger. Now this salted fish senior sister must navigate dangerous plot points, avoid death flags, and somehow survive being the villain's white moonlight while maintaining her commitment to doing absolutely nothing.