There was equal trust between the two. John didn't find the same trust with anyone else. Hell back when he was in the Brotherhood, he didn't hold the same trust with them like he did with her. John knew that she'd come fighting tooth and nail to come save him if he needed it. Side from Blob, he wasn't sure any of the Brotherhood would do such, so letting his guard down with Kitty - it felt natural.
Well, desperate to fill her with everything he had she was about to get every wish she wanted. The way she gripped his cock, John lost himself and couldn't hold it if he wanted to any further. A gasp from his mouth, and a very pointed "Fuuuck." from John's mouth was quickly followed by a twitch from his length in her as he came just as hard as he was fucking her. Not wanting to lose the feel of her, John's hand dropped from her throat to her hip so with both hands he could pump every ounce of himself into her burying his entire length into her.
"Jesus." John moaned at her while his hard thrusts slowed a bit as he felt himself empty into her. "Fucking. Christ." The words only felt like the only words that could fit the situation at hand. Every time, every single fucking time - Kitty had this way to make John see stars when he came with her. It was just another drug for him honestly, one that he just wanted to dive into more.