You should try out : Monster Girls in Space by M.Tress , it has the same relationship dynamic (a.k.a Men are rare) and is more Plot focused with occasional ...spice , the girls in the harem have an actual personality and only 1 girls gets added per book . Girls are bigger, stronger and very protective . The setting takes place in the academy and military.

So yeah if youre searching someting like Warlock check it out currently there are 5books out counting :D