Interesting in that Ch 26 of the main series seemed to directly refer to Backward Cap as a boy, with everyone, including Leader, using -kun as their suffix; yet this spinoff says its a girl.
Granted I haven't seen the raws of either, so I am curious as to which translation is right and which is getting lost with ambiguous gendered language. Or it could be like the original Banner of the Stars manga that didn't realize Sobach is a guy and drew him as a woman in error.