RECENTLY, MY SISTER IS UNUSUAL

In the romance comedy, a girl named Mitsuki Kanzaki lives with her step-brother Yuya 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 Yuya to move towards the "Gates of Heaven." — Description from AniList community (anilist.co).