She was probably involved in some sketchy stuff. I mean her mother was very lax when she raised her, not even telling her what was right or wrong. She just basically told her. "Figure it out yourself" So she did some stuff she wasn't proud of and regretted, but now...the past is behind her. Since she doesn't like to talk about it, she is probably embarrest. I mean, she's supposed to be a role model to Japanese girls. So she keeps it a secret.