Episode 4 is the only case of flagrant parallel routes through the same context. But that's starting to change and it's a bit more complicated in other cases depending on how you look at it.
In episode 5, all MCs have the opportunity to accompany Josy when she meets her father. If you accept, the MC will then have the choice to either accompany Josy to her room, or to follow Maya after she wandered off (obviously upset). You'll only get one of those scenes in a given playthrough, and the scene will only lead to sex if the MC formed a relationship with them.
Episode 6 gives the MC a chance to either tend to a sick Sage or go on a date with Jill; both options require certain prerequisites, but you can only do one. As far as we know, neither choice completely forecloses pursuing the other girl in the future, but it may have some impact and you'll definitely miss one scene or the other.
A lesser version of that involves Bella's much anticipated lewd scene in Episode 6. If the MC did certain actions, the MC will automatically accept her invitation to help clean his room (and then get frisky). If the MC did only the actions leading up to those, Bella will offer to help, but the MC can decline (and note that he did so to avoid anything more happening). If the MC did none of those actions, Bella won't call at all. In that case, Maya & Josy will help the MC clean his room if he's on their path (no lewd scene, though), otherwise he cleans it himself.
There are less clear cut examples, too. For example, forming a relationship with Maya and Josy will lock the MC out of fooling around with Jade, Cathy and/or Quinn later on. The scenes with M&J or the others don't happen simultaneously (and a number of people here complain about the restriction), but it effectively forks the content. Similarly, MCs who go on that date with Jill will automatically decline a few opportunities for sex with side-girls near the end of the episode (assuming he would have triggered those opportunities otherwise).
