The Duke or whatever rank the guy who killed her parents is, does know she is a girl.
Most other people don´t however.
He intentionally allows the MC to dress like a boy, because she likes it better than the female dresses AND because it's a huge frick you to his dad who wants him to get married.
It's his way of avoiding having to deal with all the prostitutes noble honey traps that his dad and the other nobles send his way trying to get him to have a kid to force a shotgun wedding.
Something everyone is ok with because he has a really high status.
The duke is pretty much the definition of somebody who has no sexual attraction AKA "Asexuality", so he just does it so he doesn't have to deal with all the bullshit.
XD men that weak gay bait. using a random nobody for plot. Like...what reason does he being gay plays? Why do we need to know this?. How is he being gay tight with the story?
@Goldenzeal thanks, but I wasn't talking about the duke. I was talking about Trigger and his confession to Chloe that he's gay hence why he doesn't want to get married.