artist's story of sister possessed by girl's spirit who must fall in love with step-brother

The official website for Mari Matsuzawa's Saikin, Imōto no Yōsu ga Chotto Okashiin Da Ga. (Lately, My Little Sister's Been Acting Strange, But.) manga series announced on Tuesday that an anime adaptation has been green-lit.

In the romance comedy, 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."

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. Kadokawa's Fujimi Shobo also streamed a television commercial for the manga:

Matsuzawa's other works include Hinadori Girl, Inukami!, and Sanbun no Ichi. The original Inukami light novel also inspired an anime, and Seven Seas published the manga in North America.

Source: Comic Natalie

Update: More background information added.