It had been the truth, what they discussed earlier, the fact that Navi was very much petite. She seemed even smaller when she was laying underneath him, her body so close to his own. The reason it caused any worry to even form in his mind was the fact that he had strength which exceeded any normal person on the face of the planet. He didn't want to hurt her, the last thing he wanted to bring her was pain without any pleasure.
But her actions, her responses, were indicating that it was okay to be at least a little bit rough with her. There was always a step of going too far, and he'd try to be mindful of that. When she started to move her hips against him, he knew what she wanted, what they both needed. His eyes closed, his hand reached down between their bodies, and he lined them up right. With one thrust, he buried himself as deep inside of her as he could, moaning against her lips.