When you think about it slime girls would be amazing partners. While having few flaws (like usually beeing cold or you know, beeing slimes), they can cater to any needs no matter what gender you are. They can take any shape, both outside and inside so can "fit" anyone. Truly perfect.
@FluffyCow The anime (S1) left off with them being rival actresses at a theatrical play (and also kinda for the MC's affections but we don't talk about that) so it makes sense for them to be confused :))