Life After Transformation

It's the kind of story where an old immortal is refining pills in the Celestial Court, and a yin spirit pill falls into the mortal realm. A boy is sleeping, and the pill drops into his mouth. If a woman swallows the yin spirit medicine, it makes her beautiful and keeps her young forever. If a man swallows it, he also becomes immortal, but turns into a woman, an absolute beauty.