i don't think it's either one. it can't be a harem seeing as we have all of 2 female characters of any significance. as for a reverse harem, while there are many more significant male characters there isn't any real romantic interest present.
Well, besides the princess is only fourteen. I don't think she's even considered anything romantic, yet. She's more concerned with being a leader right now. I mean, that's the only reason she shanghai'd the strategist. She's definitely friendly with him and respects him, but I don't think she feels anything romantic.
I've read the 3 first volumes. Nothing really screamed harem, however there were several that have a romantic interest in Regis (although apart from Diethart no one spells it out and Regis really need people to spell those things out for him). A lot of the time the gender roles are swapped quite a bit so Regis is the damsel in distress that the women are trying to protect LOL
So, is this a harem or reverse harem? （￣へ￣）