Because I'm the Goddess(2003)

Kamisama da Mono♥

Goddess Pandora was sent to Earth to collect "gifts" that were spread among humans. She has a nice body that can temp 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.

(Source: Tokyopop)