If I remember correctly, there are four. First is the masturbation in the ship, second is the random guy in town, third is the one from Leaf's race, and fourth is with Leaf in the temple.
Talk to the engineer by the industrial area again, the one who first asks you to take out the monsters there (I did it naked, but not sure if you need to). He'll ask you to do something, then he'll ask you to do something else lol.
