Aa! Megami-sama!

Based on the anime series Ah! My Goddess, the game follows the story of a Japanese high-school student named Keiichi, who has accidentally summoned the powerful, yet very lovely Norse goddess Verdandi (mercilessly misspelled Belldandy in the game) and pronounced a wish to stay with her forever. Now the gorgeous goddess has become a part of his life, and the two find themselves involved in constant misunderstandings and comical situations, yet also develop feelings for each other...

[From Moby Games]