Aoisama ga Ikasete Ageru

From MangaHelpers: Terahara Yuta has the ability to see ghosts and to understand what they're thinking, but he can usually do little about them. He seeks out the genius medium, Sasagami Aoi, and convinces her to take him on as an apprentice. He is determined to become skilled at helping put spirits to rest. Aoi is a cute and domineering young girl who often gets possessed by the unrestful spirits. This tends to result in tons of unfortunately erotic and/or unclothed situations between the two of them, as Yuta attempts to satisfy the spirits that take over Aoi's body!