Don't worry about it, it's fine, I probably didn't pay attention at the start. For me it was briefly skimming through summary to see names where one sounds feminine and the other masculine, so I then incorrectly assumed their gender through superficial identifiers like gender expression, clothing and eyelash length. The comment is not meant as a critique/feedback, just a personal anecdote that felt oddly fitting to the story told. (Halfway I also remembered that the History log shows it with character names.)
Thank you for sharing where the character inspirations came from. It's really fun to look them up.
Yes, I only found out that Ceferino is non-binary when they explained that to Rubina. That felt very real to me, that older (queer) people still learn so much more about themselves and the world. I guess I'm low-key an old person too, haha, as I came with certain biases, and I enjoyed the subtle reminder not to judge a book by its cover!
That sounds cool about your new VN. Good luck with that!