A central character of the Aa Megamisama universe, Keiichi Morisato dialled the goddess helpline by mistake when trying to order pizza and summoned Belldandy. She grants him one wish, which he uses to wish she would stay with him forever.
Keiichi is a university student and as such doesn't really need the problems that being romantically involved with a goddess bring. Two of his largest problems are Belldandy's sisters, Urd and Skuld.