Kazuki knew that everyone's personality was affected by multiple factors.
Mikito Hanzawa's parents died when he was a child, and after he grew up, his brother was always out working. It seemed that both of them were interdependent, but due to work reasons, Akie Hanzawa rarely took notice of his younger brother's daily life.
Therefore, external environmental factors were crucial to Mikito Hanzawa's development. He developed a submissive personality and his attitude of just scraping by as the days passed. Kazuki was sure that Mikito Hanzawa must have gotten used to being bullied during his years in middle school.