Experiment. It was such a tempting idea, and yet, Harry had never been comfortable with casualness when it came to sex or romance. He'd tried to throw himself into a moment at Halloween, but Harry was fairly sure he'd have panicked eventually. Regulus had been as close as Harry had come to casual sex, but he had still insisted on continuing as friends with the other man. He couldn't let go completely.
"I know I feel better being able to write to him again, so I guess I have closure. But I think I've already gone through my experimental phase," he said with a wry grin directed at Regulus' back.