I actually played it out of curiosity: the tone is definitely darker than Inyouchuu, the protagonist has memory issues and straight out hears voices in his head, the only character with a more upbeat attitude is the assistant of the protagonist, everyone else has the usual "murder mystery aura" around them and there is definitely ghosts and possessed dolls etc.
The story is about a private detective (the protagonist with memory issues and voices in his head). We learn that he used to work in the police until something very thraumatic happened to him 6 years ago, although they keep mystery around it. He has a recurring nightmare about being a doll while someone with a familiar voice rips out his intestines. Even though his job a p.d. doesn't pay much, his assistant basically works for free because she wants to learn to be a detective herself and she seems to admire the protagonist.
One day, they are called on an isolated island, inhabited only by a rich family and their servants, to investigate a murder case. On their way there they also meet a female police detective who used to work with the protagonist 6 years ago and is now here with a younger collegue to investigate the crime.
Once arrived on the island, the protagonist feels like everything is too familiar and starts having flashbacks. In addition they realize to be stuck on this island without telephone (not even cellphones work) with a potential assassin roaming free or maybe something worse.
As for the sex scenes, many of them seem to end in gore, with innards being torn apart and so on... although the ones in the demo seem to be less extreme than i though, but based on the preview images they are saving the worst for the main game.