It happened in Toronto this time when she was singing on stage as special guest in a singing competition; her nipple slipped for a few seconds before she noticed it. To make it worst, the event was live, and somebody managed to record the clip and uploaded it online.
Some people actually suggested that she did it in purpose, which we think is too harsh. She needs to learn to be more careful though; it’s accident if it happens once, but it’s plain carelessness if it happens again.
[Image credits to Sohu.com when Yumiko was back in Hong Kong airport]