At this point, I really have to ask...dare desu ka? As in who? I'm an idol fan and I've never heard of her.
Googling her name now (both in English and Japanese) is just going to give you a flood of news reports on her pregnancy. But there's sparse little else info about her.
Her JP wiki page is really sparse on info as well. Don't know who she is, and have little reason to care.
That said, there's something distinctly wrong going on here. Unlike some other idol fans, I'm not averse to the girls dating and having a life outside of their careers but this actually crosses a line. Its similar to a teacher having a relationship with a student and I don't mean at high school level. Even in a university where age is not a factor, this sort of relationship is strictly forbidden on professional grounds.
That guy's career is pretty much finished. No one else in the industry would want to hire him to manage their idols as they now know he can't keep it in his pants.