Answer: Foil.
Step-by-step explanation:
A foil is a literary character that exhibits characteristics that are in contrast with those of a different character. Usually, the foil is a secondary character who contrasts with the main character to heighten specific traits or even the importance of the principal character in the story.
Wei-Chen is a foil in the sense that he´s fully Chinese, whereas Jin Wang is self-conscious about being Chinese, and wants to seem white.