月は切り裂く 〜探偵 相楽恭一郎〜

A detective adventure game in the veins of visual novels featuring a third-rate private investigator, Kyouichirou Sagara. After having a few drinks too much, he hits off with a woman he met in a pub and ends up going to his room. However, upon coming back to his senses, he barely remember how he got here or where here is, and to top the suspense, he finds an unfamiliar woman on the bathroom floor. Trying to think of a way out of his predicament, he is caught by the police just as he was about to step outside. As he skillfully wiggles his way out of the interrogation room, he has a case to work on, something which will get more and more complicated as the story progresses.

[from MobyGames]