Keiichi Morisato is looking forward to university life. But in reality, he has no luck in anything, and he has trouble with clubs, love, etc. The truth is that he has an unlucky star above his head. One day, Keiichi is stuck watching the dorm while his sempai are away, and has a mountain of chores to do to boot. But Keiichi is a good-natured person, and is set about doing his duties. As he is about to finish his final chore, he makes a phone call to his sempai. But the words that came through the receiver are, 'Goddess Help Line.' Shortly afterwards, a beautiful goddess named Belldandy appears in front of him from the mirror of his room.

When college student Keiichi Morisato dials the wrong number while ordering for some food at his dormitory, he accidentally gets connected to the Goddess Hotline and a beautiful goddess named Belldandy appears out of a mirror in front of him. After getting kicked out of the dorm, Keiichi and Belldandy move to an old shrine and soon afterwards, Belldandy's sisters Urd and Skuld move in.

It has been three spring-times since Belldandy came to Earth to grant Keiichi one wish. Things seem to be fine with them while living in the temple with Belldandy's sisters Urd and Skuld, but little do they know that a fallen god from Belldandy's past has escaped from his lunar prison. He has plans for everyone which do not include what the goddess and her human lover wanted for themselves.