If i remember the spoilers i read right, it's technically a harem in the more traditional sense, aka none of the women actually sleep with the archduke (harem's didn't always mean sexual favors and such, in some ancient cultures a harem could be similar to a women's boarding house or a convent), it's a home for young women the archduke saved, i'm not sure why the FL isn't in there but it might be consideration for her past and to avoid any kind of misunderstandings.
Haha agree, she gives Resemonds vibes x 1000, anyway, I like how clear and straightforward our ML told her to get lost. xD Poor MC though, how uncomfy, lol.
I really like his response to that red haired girl, he's very straightforward and clear. Much better than wishy-washy "niceness" that's easy to confuse as having a chance