Let's face it: Sex sells. It doesn't matter much as to what exactly is doing the selling. In the case of Dead or Alive Paradise, what sells is dozen bikini-clad DoA vixens as they vacation on New Zach Island, a fictional tropical beach resort.
The basic concept of DoAP is simple: take on the role of one of the DoA girls and play a minigame-driven semi-date sim with the ultimate goal of wooing one (or more) of the other girls to allow you to take private photos of them. It's a concept that will make pre-pubescent boys squirm while at the same time making full-grown men feel like dirty creeps. Good thing DoAP isn't a very good game.