The Legend of the Demon God tells the story of a hero named Luo Shen who crossed an alien world and became a slave. There, he met Bai, the daughter of the White Devil, and became a close partner with him. In the following story, I learned that Bai was about to be forced to get married, and his hair suddenly turned white.
In Chapter 36 of Volume 2, there is such a description: "This is the first red dress of Luo Shen and Bai thirty miles away. In order to watch Bai become another man's wife, he sat here cross-legged alone, waiting for the arrival of the red dress. " Here also describes the protagonist kneeling, hair turning white and other plots. So I guess the plot description you provided comes from this scene in this novel.
I hope my answer can help you.