4 hot wave. I don't consider Kumi to "experiment" like apparently other people do from looking at her official thread, but she at least did try out some rock and it worked really well for her.
It also had JUICY which IMO was better than any of her other songs of that style since 4 hot wave, I'll be there which had a really pretty PV and is a nice summer song, and With your smile which is catchy but unfortunately started the trend of whatever songs it was people all think sound alike.
FREAKY wasn't very good IMO, since the only memorable song from it was FREAKY itself (which I never, ever listen to). The other songs were okay, recycled, or just plain bad.
And I didn't like a single song from MOON so I don't have anything to say for it.
