The reason why this can happen is because of the transformative journey that Jin Wang is on. At first, Jin Wang is ashamed of being Chinese, and wants to appear as white as possible. Wei-Chen is fully Chinese, and because of this, he is a foil, as he is a character that highlights the characteristics of the protagonist by contrasting them with his own, which are the opposite.
However, as the story progresses, Jin Wang becomes even less similar to Wei-Chen, as he kisses Suzy and as he transforms into Danny. Jin Wang, therefore, not only contrasts with Wei-Chen, but is in open opposition to him. This makes Wei-Chen the antagonist.
The words such as blood-bedewed and corpse-like in the phrases given above give off a sinister tone. The words blood and corpse relate to death, a dark atmosphere, or hints that something threatening or harmful is about to happen or has happened. The word "sinister" best describes the tone used in these phrases.
I'm sorry i just want points but if u need someone to talk im here :)