Belldandy's basically the perfect person.. only she's a goddess. And of course she's not completely perfect, coz then she'd be annoying! All in all, Belldandy's a real sweetheart. She's kind, she's thoughtful, she's sweet, and she's got those kik ass powers..
So what's she doing with Keiichi? Good question.. Since Belldandy is the goddess in charge of granting wishes, Keiichi sorta stumbled into asking her to stay with him forever. And who's gonna complain about that? So she ends up keeping house for him and going to college with him and joining the Auto Club with him, which shocks his classmates coz.. well.. Keiichi ain't exactly a ladies' man and Belldandy is.. in comparison a total babe.. But despite their most desperate "wooings" no one can take Bell-chan away from Keiichi (did I mention she's way loyal?).