Previously a newscaster, Mizuki decided instead to pursue the path of becoming an idol. She's nearing her 30's and is a bit self-conscious about that, taking very good care of her appearance, and eagerly competing with her younger comrades. Her insecurity about her age stretches into not having a boyfriend or husband.
She acts as a role model for some of the idols. For example, she taught Karin Domyoji how to speak more clearly and smoothly. She is very mature and hard-working and often tells the Producer that he can rely on her whenever he wants. Her hobbies are cleaning and doing laundry, and she even offers to clean up the Producer's room in one of her SR card comments.
The staff tried to tell her to simply be herself during her drama CD interview, when she pretends to be a teenage girl or sexy temptress, because of her fears of being too old. At one point, she even tries to steal Nana Abe's "eternal seventeen alien" shtick, but it made the staff angry.
(Source: Project iM@S)