Magical Sisters Lulutto Lilly (Series)

Fuu Nonoyama and Rui Nonoyama are sisters from a "land of magic," who were once on terms with one another, but have drifted apart. Suddenly, they are given magical powers by two cat-like spirits, Uguisu and Azuki, allowing them to transform into magical girl idols. However, there is a catch: these powers only last for a year and they cannot tell anyone that that magic exists. While neither Fuu nor Rui knows one another are magical girls, they soon begin their careers as idols. (Source: Wikipedia)