The tension coming from him not wanting to accept he loves her dominance and authority. And the Captain not wanting to appear weak in front of her crew! Maybe he's a recent addition to the ship and before him the crew had sworn off men for anything but momentary pleasure? As he accepts his desires and who he is, there's the struggle with how he can be strong and a warrior but also submissive. Societal gender expectations could make him question his masculinity. It would be great if he eventually got to a mental space where he is confident in his relationship with the Captain and their roles in it while also being the strong warrior he always was. He would relish and cherish the uniqueness of the relationship as being both necessary and a reflection of the amazing Woman he feels fortunate and lucky to devote his life to. And the Captain could get to a place where she realizes her love and affection for a man doesn't take away from her strength, independence and authority.