Let me explain the concept a little bit better. Let's say you chose to play as Landon. You're lost with Scarlett and you're doing sweet and nasty things with her. You are playing just as Landon. That means that somewhere else Liam is lost with Ashley and Velvet. Does that mean that Liam is having sex with Ashley and Velvet? No. They are just trying to find their way back home. At one point, you (Landon in this case) are reunited with the other characters. This gives you a chance to seduce Ashley and Velvet and have your perfect harem happy ending