This could go so many ways, maybe he is really bad and wants to kill him to add him to his collection or maybe we could go with a more wholesome one and he is just a monster enthusiast but being the crown prince he wasn't allowed to be near real monsters.
I was kind of worried about a potential axing last chapter with the rapid development of Mino's ability to speak language, but it seems like the story is just moving in a new direction, which I can appreciate.