Futakoi Alternative (2005)

There's Rentarou, a 21 year old good for nothing dropped out of college guy, who calls himself a private detective. And there are the Shirogane Twins from the first Futakoi series, Sara and Souju who kind of "work" as his assistants. This is where the action, comedy and misadventures start and lead our trio from one pinch into the next. [From Anidb.net]