Whenever Shin thought of Ibuki Sumire, he would recall the time he spent observing her.
She truly is different from what he pictured. He thought she was an emotionless girl someone who didn't have any emotions. It was only natural for him to think that because their past aside. She never reacted to any of the cruel things he said to her. No matter how cruel his words were, she didn't react to them. No that's not why he was so cruel.
It frustrated him, seeing her like that. It was frustrating watching her act exactly like a doll with no emotions. There's no way because the girl who helped him escape that day looked so frantic and desperate. That's exactly why, despite the feelings of anger he felt that day, and he didn't hit her.