Hitsugaya saw the level of intimacy between Artemis and Haku, and decided it was time for him to leave. Also, despite Hitsugaya's efforts, his presence also seemed to be having an adverse effect on Fowl.

"Excuse me. I need to continue my search," he said, then calmly walked away, blending into the crowd.

Meeting with Hughes was more important than smoothing over feelings with a stranger. It might have been a cruel way of looking at things, but Hitsugaya's position demanded that he focused on the bigger picture.