He followed her lead and kissed her back. It wasn't quite the same level of desperate but it still lingered, fueled by the years he had wanted her and never had the nerve to do anything about it. Purposeful and not something either of them could brush aside as an accident, or just a physical reaction to being so close to each other. He knew in the back of his mind she could still push this way, him away. That in the morning she could still try to excuse this away as them letting the situation get the better of them - but he knew without a doubt right then that he wouldn't let her. There was no going back, not now.
"You couldn't have known," he assured her again, as they parted and she spoke. It was soft but not without conviction behind the words - and just like he knew she would spend as long as it took to bring him back to the person he used to be, he would spend as long as it took to convince her that none of this was even close to her fault.
His hand moved from its spot in her hair to her face and his thumb rubbed against her cheekbone. "I'm not going anywhere either." He was done, done trying to convince her he was fine when he was anything but, done trying to pretend like what he felt for her was nothing more than friendship, that he didn't want her the way he did. He didn't expect that this would magically all be better, that either of them wouldn't stumble or screw something up along the line. They were real people with very real damage and flaws but they were bonded in some way that went beyond the normal lines of friendship or partnership and Steve knew that was worth seeing this through. He smiled softly and tugged her back in to kiss again. The hand that was wrapped around her moved to the hem of her shirt, and there was a brief hesitation before he slipped his hand under and let his palm press against the warm skin of her back.