I also think Shingo and short hair understand the expectation of male/female romantic relationship (even if they have differing opinions), in contrast to Touma, who doesn't seem to understand that dynamic. Or willfully ignorant? I'm pretty sure Touma is gay, but I get the impression he doesn't really understand that part of himself.
Mami is clearly a disaster asexual or something like that. I'm rooting for her now.