Zhan Qishao
Still...it's only explained that FJ dressed as a boy for money but there're no detail reasons. This... is just my idea, in order to inherit heritance/company/whatever is it.... her mother has been hiding FJ true gender... if his father doesn't know if FJ is a girl? Is there any explanation that his father knows that FJ is disguising as a boy? So far.... people around FJ are just angry for her being so flirtous around men.