No, you're not on your own. Voltage USA games also have a dedicated fanbase, just not really present here, that's all. My favorite voltage games are n°1 Speakeasy Tonight, n°2 My Killer Romance and n°3 In Your Arms Tonight, in that order, so yep while I discovered Voltage with the Japanese brand, I do prefer the recent US ones (not the old us ones like the thief adaptation that burned my eyes...).
I couldn't help with Nathaniel because I thought his route was boring and I can't even remember if I got the HE or not, but if you need help with the other guys walkthroughs, shoot. I can be of help.