Alrighty, figured out how to get the nomad route.
As
@thkvl mentioned, there's a certain level you have to reach. Not lewdness, but
HOMICIDE!
Basically, you go through the common route for the first chapter, failing a certain amount of boss battles (dunno the exact number, I just failed them all), then you get into the Resistance route, working for the hero guild in the slum.
Anyway, onto the critical bit: Once you're working for these guys the dungeons you'll go to will be populated with a mix of monsters and humans. You're gonna want to fight the humans, then every time you beat one you get a choice to spare or kill them. Choose the second option (the one that says トドメを刺しておく) and you'll add to your number of murders. After 10, my "Evil Level" went up, and according to the guide you just need that at level 3 by the time you hit the end of Ch.4 in the resistance route to go down the nomad path. Can't confirm that it's just 10 kills per level, as I'm working on it now, but just wanted to let y'all know that's what you have to do.
Once I get to the route I can post a save here if y'all would like.