I sorta like the sound of “ur-yo-mums”.
Were I writing this comic today, this would be worded differently. Uryuoms only have one sex (physical), but gender (mental) is more complicated than that. It gets a bit complicated when one considers that they’re not human, but there are uryuoms who would describe themselves as masculine, feminine, neither, alternating, etc. by human standards.
I’ve had a history of favoring the word “gender” over “sex” because, frankly, the latter has multiple meanings and I felt less awkward using the former. I want to encourage the gender in reference to mental and sex in reference to physical approach, however (even if it’s not really quite that simple), so I’m likely to phrase things differently in the future regardless of whether it makes me feel irrationally uncomfortable at times.