This Hentai OVA is based of a Visual Novel of the same name but just to keep things short, my advice is don't watch this and play the Visual Novel. The Visual Novel is about a Private Detective contracted to solve a missing person case from an All Girls School, set in the 1950's Japan, but he later finds out that this case bigger than it seems, The game has elements of Horror, Detective Thriller, Psychological and Moral aspects that were ALL LOST in the Hentai OVA, the only thing left in the OVA is the very basic story line and all the H-scenes and H-sceneswas my least favorite part from the Visual Novel.

In the end this kind of story needs an at least 12 episode anime to fully utilize it's story and potential and not a hentai OVA which only focuses on the sex scenes, which was never really the focus of the Original Source Material.

Ratings
Visual Novel 9/10
Hentai OVA 2/10