I think the fem character sexuality config is broken. I have one fem MC who only has sex with female characters (nymph, female bandit, etc.) and zero sex with male characters (and no sex with slimes and other indifferent creatures), yet she is still "bisexual." She's had so much sex, she's an "expert," yet her sexuality is still unchanged... :/ (Edit: I was trying to make her a lesbian. I guess if you want a bi fem mc, just only have sex with female characters in the game and no sex with men? I dunno...)