I was trying not to spoil things but yes, he's intelligent and has picked up a human language pretty well. Not fluently as you can see by his stilted way of speaking. There's a dictionary found in his cave that he has used to study. Merfolk are another intelligent species but they are still wildly different from humans. Consent might not even be a concept that exists in their culture. Agares is as gentle as a lamb compared to the violence the other mermen inflict on their human mates...that they capture by force. In the novel, these people seem absolutely traumatized by the experience. It's disturbing.
Did merman even know something called 'consent' ? It's human word.... The thing might not work the same for mer creatures....what if playing-hard or fighting is their call for mating (lol) if so MC is acting willing in his eyes we shouldn't use human thinking on ML pov