I have been wondering about Ayu's boobs (that sounds weird) they definitely got larger from 2004 onwards and a lot around 2008 when her weight fluctuated (not a lot, but enough to show on such a small frame) and she wore dresses showing cleavage more. I never thought she'd had surgery though (totally fine if she has! but she never seems to have the time off!)
They definitely seem to have perked this year but then looking back at the Wacoal ads, maybe not? If I'd had them done, I wouldn't be doing acrobatics on stage... I wonder if it was done previously and she's wearing push up bras more now?
Actually, looking at this from the GUILTY booklet

And even MY STORY
I put on a cup size in my twenties and a bit more when I put on a bit of weight so maybe it is just body fluctuations?