What do an alien, former ninja, weak telepath, and boy pretending to be a girl have in common? They are all classmates at Kashihara Girls' Academy, and they hide their true identities from the world. Rikka, Chiyo, Sekine, and Tsubasa seem like the best of friends, but they each harbor a monumental secret that they cannot reveal, no matter what. In order to continue masquerading as normal middle school girls, each of them must invent creative ways to conceal their true selves. But that is easier said than done, as the four students end up entangled in numerous shenanigans along the way.

One year after goddess Belldandy emerged from Keiichi Morisato's mirror and promised to stay with him forever, a new threat to their happiness emerges, one that could end the contract between Belldandy and Keiichi.

For centuries, a god named Celestin has been imprisoned on the moon for betraying the kingdom of Yggdrasil. Released by the fairy Morgan Le Fey, Celestin travels to Earth to reunite with his former pupil, the goddess Belldandy. Things go awry as Celestin erases Belldandy's memories of her boyfriend Keiichi and uses her as a catalyst to wreak havoc on Earth and Yggdrasil.

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.