Sometimes with Ayu I can't decide if she is truly this dedicated to the fans and her career or if she is just stubborn and careless.
I think fans would rather have her rested and feeling great to give a high quality performance. Performing while sick is only going to hurt the quality of the show.
Ayu performs so often every year, if she cancels a few dates there will still be plenty of chances to see her in the near future. But Ayu is insisting so.
