Mahou Gyoushounin Roma

Roma is a mysterious girl who is on a mission to collect "human greed" through the use of various magical objects that have unique powers. When humans use these magical items to satisfy their own personal emotions, such as love, their greed level increases and Roma is able to steal their excess greed.

The people that use Roma's objects seem to always let their greed destroy themselves, putting themselves in a worse situation than before.

(Source: MangaHelpers)