Because I'm the Goddess (manga)

Pandora is a busty goddess that was sent down from earth to collect gifts, which reside in women. But, when Pandora uses her powers, she turns into a little girl. Her only savior from hersmall form is Aoi, who only sticks around because he finds her small form charming.

Pandora is the ultimate and voluptuous sent to earth to collect gifts small fairies that been spread among humans. Collars they use can control humans then she meet Aoi while trying to Mattsun a genderless cat out of a tree her top rip protect her from onlooker's. When she use's her power her bust shrink and become a young girl she need Aoi to recharge and become normal again with a power of a kiss. She love him but he's being stubborn while Aoi trying to stop bad situation without himself using violence. Pandora get jealous very easily.