Final answer:
Mari and Eri are presented as opposites in the narrative to explore identity and societal expectations, highlighting the complexity of characters and themes within the story.
Step-by-step explanation:
In the context of the chapter, Mari and Eri are presented as opposites to showcase the diversity of characters and the complex nature of identity in the narrative. Authors often use contrasting characters to highlight particular traits and themes. In this case, the stark differences between Mari and Eri underscore the notion that people are multifaceted and cannot be easily categorized.
This contrast might also amplify the story's exploration of authenticity, as each character could embody different aspects of human experience or represent differing societal expectations. The readers are invited to contemplate the significance of these contrasting personalities and how they might relate to the broader human condition or specific thematic elements in the story, such as the masks we wear and the pursuit of individual identity.