Thanks for the update!
I get a feeling that the master at night is the prince she's looking for during the day. As for the master of the day I think it's going to be the prince's fiancée. He's been in hiding and avoiding her trying to break off the engagement and so she needs to find him. Also if this was this case it would make the story rather interesting and complicated as it would put the MC in the middle of her masters' conflicting goals.