They're not lesbians cause they're not only attracted to females, they all just happen to like the very cute Argen who just happens tobe a girl.
There are several characters that have alluded to not liking men, and most haven't expressed a preference other than women. I think it's a cute story, I just think it isn't categorized correctly.
Laila tried hard to deny her feelings for Argen at 1st even now she's uncomfortable about ho she feels. Thats not the actions of someone who's openly gay acts and no one accept that pervy vamp said they are attracted to woman.
This really should be shoujo ai. I get that the MC has the excuse "he's only into girls because she used to be a he" but all the other characters are lesbians (except darling Zeno of course).
I can only assume that the target audience is male since the author did everything to make sure it isn't Yuri. As fluffy as the characters are, I just don't get that warm soul nourishment vibe found in Yuri.
┗( T﹏T )┛
If you don't know what I mean here are two fine examples:
http://www.mangago.zone/read-manga/jewels_m_k/
http://www.mangago.zone/read-manga/from_aiu_station_on_the_hiragana_line/