Oppai Slider 2
In Oppai Slider 2, the player can choose between three different scenarios, in each of which a girl plays a different role: a nurse (with the player as the doctor), a maid (whose master is the player) and a "sailor", who is simply a girl that the player has to teach how to swim. It's actually the same girl, called Asakura Koyori, in three different stories.