Not enough information to answer the question
What is the story?
If I know what happened in the story I can help.
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.
