Please DM me with info on where you got the download, and then version and what is happening, and I will try to help out if I can.
Well, it's not exactly an easy question to answer, as the characters do have some agency in their sexuality. I don't want to give many spoilers for the plot, but through Episode 3, Nikka, Kani, Rachel, Samantha, Irune, Oluna, and Rin (who's not female but some people have trouble with non-binary characters) all will appreciate the female commander (even if the option isn't there yet).
Of course the servants you have available to you will all be happy to please. As you move through more episodes other characters will become available and more one-of characters are planned. Now, whether they remain (or any character remains) in a relationship, could eventually change based on your choices.