I loved the first two couples, but my interest dropped like a meteor in Russia once the third girl came in--completely unappealing. Then the fourth came in, and she was no better. Fifth was also unappealing, so I left the manga alone; didn't bother with the anime.
As for Nakamichi and Karen, well, it's probably as someone said earlier: her eyes changed color. The question is who's got her now? (The color looks a bit familiar; if it's whom I think it is, that'd be one hell of an ugly twist...) Whomever it is, and when she's given the boot...I hope Nakamichi could actually grow a spine and take this girl--because that Greenhair is waiting in the wings. I'm surprised he didn't show up instead of Nakamichi when that door opened and Karen heard "I'm back" before Nakamichi fell out on the spot.