Original creator (manga) : Mari Matsuzawa
Plot summary : A girl named Mitsuki Kanzaki lives with her step-brother Yūya after her mother remarries. One day, Mitsuki is possessed by the self-proclaimed spirit of a young girl, Hiyori Kotobuki. Hiyori (in Mitsuki's body) must fall in love with Yūya to move towards the "Gates of Heaven."
Note : Matsuzawa launched the manga in Kadokawa Group Publishing's Monthly Dragon Age magazine in 2010, and Kadokawa is publishing the fourth compiled book volume this Saturday, December 8.
The plot sounds interesting, but the screenshots I've seen proves me that it's going to be bordeline hentai. Still, no matter how obnoxious the plot looks, I will try the first few episodes to see if it's really good.