How to tag "Otoko no ko" characters when it is a spoiler?

I am asking this as a preparation for some art. I often upload art of the characters from SINoALICE. Issue is that one of them, Gretel, is really Hansel crossdressing as his sister but it is also a plot reveal. Although this reveal is common knowledge within the fanbase now, I am unsure of how to tag it properly at this point. I have tagged it using female pronouns up to this point, but they are planning to release reverse trap jobs soon which is gonna cause all kinds of headaches with Gretel/Hansel.

The gender is like unavoidable spoiler imo. If someone searches this character here on danbooru, it would be equivalent to searching the character on his wiki page, which would tell the character's gender anyway.

Gender is generally an unavoidable spoiler, so such characters are simply tagged as their actual gender.