For me it's between Geminis and Sai, partly because I love glasses and the whole 'smart girl / tech girl' trope. It also doesn't hurt that Sai had the most character depth.
But actually it's clearly Geminis because she's not just super hot but oof that stuck up prideful attitude is soooo my thing. I think Geminis made me more gay than I already was lmao...
Also, while it's understandable people have complained about Geminis not getting enough 'action,' for me it's perfectly fine because she got restrained more than anyone else and that's more than enough for me! The alien parasite thing pinning her hands behind her while sucking her boob is hotter than any scene imo!
The only thing I don't like about the girls is that none of them really seem to get embarrassed even when half naked or in very compromising circumstances. I feel like they should at least try to cover their chests when talking to each other, lol.