Read manga: Kami-sama Damono

manga
Summary:

Goddess Pandora was sent to Earth to collect "gifts" that were spread among humans. She has a nice body that can tempt anyone who looks at her, but when she uses her powers, she shrinks to a young girl's body. The only way to gain her power back is to kiss her reluctant peon, Aoi.

Loosely based on Greek myth.