In Obasan, the language derives from the main character Naomi. She’s the first-person narrator, so she holds the power to choose the words that shape her own character and the characters she interacts with. Naomi does not use this power to give her character a perfect or excessively flattering shape. Instead, she uses the language of violence to demonstrate her faults and imperfections. You might want to review chapter 11 and the way in which she represents herself as responsible for the death of the baby chicks.
You might also discuss the ways in which Obasan relieves the pressure on Naomi to shape the characters with her own language. You might talk about how Aunt Emily is allowed to use her own language to shape her own character with excerpts from her letters. Aunt Emily's language involves the language of war, fear, prejudice, and helplessness.
The language of war also shapes the characters in The Wars. It informs the development of Robert and the ways in which his character becomes less innocent yet still committed to his principles. You could claim that the language has a somewhat circular movement to it. It starts with language about horses and animals, and it ends with Robert’s enduring commitment to the safety of horses and animals.
Finally, you might note how the absence of language shapes the characters in both novels. You could talk about how Naomi’s inability to describe what happened to her shapes her. You could think about how Robert’s inability to use words to describe certain feelings—particularly his feelings for women—shapes his anguished representation.