Sister Heroine Pretty Minette (@OZ)

Rina Kanzaki lives with her 2 years older brother Takeshi.
One day, she saved a white cat being attacked by a strange monster in a park.
The cat turned out to be Minette, the princess of the cat kingdom.
She was told that her kingdom was invaded by monsters and now they are planning to take the human world as well.
To save the world, she decided to fight as Pretty Minette, a united form with Minette.
However, there was a little problem… Her libido became strong!