I heard that he is indeed the ML
(But if the spoiler is true or not, we still need to find out)
Well she wasn't okay with having a child slave to begin with. She bought him to free him, then the attack happened and she assumed he'd run away only for him to follow her home in hopes of being killed. She's "keeping" him so that he doesn't try to attack the manor again because then the duke will really kill him. And the persona of being "an evil slave owner" is to make sure they don't fall into the "obsessed slave" trope. And I doubt he finds what she is doing mocking because he knows that she is trying to wear a disguse, which is why he mentioned having the "eyes of truth." The whole reason she disguesed herself to begin with is to avoid that misunderstanding, she doesn't know he can see through it. So what would you rather she do? Keep the child safe and sound and well fed under the guise of being a slave or let him free so that her dad can kill him?
Don't y'all think is kinda weird how fast she adopted being okay with having a CHILD SLAVE like she was never weird out she was like yep this is totally normal also the whole slave thing in general is a weird trope to shove in like the author didn't have to do it but yet here we are. I wouldn't be surprised if he turns out to be the villain like if you were he one day she threatening you the next she's playing nurse I would think she's mocking me who you not. Also what's with the double standard in manga if the genders were reversed it would be weird and creepy but when a girl does it is silly haha I don't know. Can someone please tell me if he is the ml because if he is I was have to drop it