Not sure why she would be fixated on him after all these years. I mean, she tricked him about going out once. Then he got tricked twice more by two other girls, meaning he showed interest in other girls while they were still in the same school, and she was presumably not clinging on to him. Then they changed schools and didn't meet or contact each other for years. Then she got in trouble, transferred to his school, and now, even though there are plenty of other people showering her with attention, she decides to cling to a "childhood friend", whom she knows she hurt (that's probably what the embarrasing story she's blackmailing him with was in the first place). I can understand Ayame being clingy when she had no one else, but this girl is shown being popular.