"They... don't mark gender, linguistically - or culturally to the point where at least a computer program, if not necessarily a human local, can figure out their genders to mark in English."

"If you tell me I can store the information for future accurate marking in English."

"I'm a girl and Xander's a boy. I've been mentally categorizing most of the people I've met here but I'm less confident in my assignments if I have to assume that clothes and... makeup and posture and stuff aren't going to be reliable signals in this society."

"This must make dating really complicated."

"It is not clear to me how dating is simplified by the categorization scheme. People are capable of visually assessing whether other people are attractive to them."

"I don't wanna date dudes even if they're in really convincing drag!"

"Drag being our word for dressing in a manner conventional to the other sex."

"Not wanting to date people who are not capable of unassisted organic reproduction even if they perfectly resemble people who are, seems like a very reasonable instance of the common preferences to only date someone who shares interest in your favorite activities, favorite sex acts, or plans for childrearing, but we also do not have binary classification schemes by which people signal those other things to the world at large. It is typical to go on dates and talk about them."

"I don't even wanna go on a date with a dude and then find out he's a dude! I'm not gay!"

"What a pity you aren't magically capable of determining that literally nobody in the entire universe is attractive, Xander, poor you."

"Sorry."

"Can you provide some more contextual uses of 'gay'?"

"Gay is a neutral-to-pejorative term derived from an archaic word meaning 'happy', for people who are exclusively attracted to members of their own sex but it has bleedthrough to nonexclusive cases. I'm gay, informally, but the technical term for me is actually 'thaumosexual', since I'm not attracted to nonmagical girls, only to other magical girls - that's something that happens when we accept magic, I was straight before."

"And straight is -"

"Opposite of gay. Most people're straight."

"Is the opposite of exclusive attraction to one's own sex non-exclusive attraction or is it exclusive attraction to sexes not one's own?"

"We'd generally phrase it as exclusive attraction to the opposite sex. Both sexes is bisexual, I don't think it's the opposite of anything."

"Attraction to no sexes?"

"Asexual, I think?"

"Like bacteria?"

"Yes, Xander, they divide in half."

"I am attracted to no sexes," says the tablet happily.

"That is not surprising!"

And they arrive at an imposing, cool stone building in a big courtyard lined with food trucks and full of people. The guards escort them in. 

"Nice place."