Ernest gave her a look of slight disbelief, but didn't bother protesting back when she said it wasn't crap - he would beg to differ, but insisting he was in fact a total pain in the ass probably wasn't going to do him any favours in that exact moment.
He moved easily with her, happily letting her position them, arms moving around her instinctively. What she was saying was fair, but there was a certain heaviness to it. It was an automatic instinct to want to deny it, to claim he wouldn't do anything worth keeping a secret over, but he knew he would be lying to himself, and she knew him better than that. This was the sweet point, this was the easy part, the highs of love when it felt like everything would be just perfect. But of course he knew what his track record was like, and he knew there was the very real, very likely possibility that he would make the same mistakes all over again.
So, there was a moment of silent contemplation following her request, but he was thinking. It would have been less sincere if he had just jumped to agreement without a thought as to whether or not he could promise such a thing. But she said she would never leave him. That was the part he had to focus on.
"Okay," he nodded after he'd considered it. "Yeah, I can do that," he confirmed more definitely.