Ai is a woman that born deaf, she always got bullied when she still a student. She then got married with your dad but it didn't last long because your dad was cheating. Ai always being sweet at bad treat. When she want to communicate, she was a bit stuttering and struggling to speak since she was a deaf person. And when she want to understand, she need to look at their mouth and read the word they speak. Whenever you want to call her, she would not hear it. It's like she ignore it but not.