Killua Zoldyck was an assassin meant for killing. One day as he walked outside, pushing the doors open as he was mad, there were neighbors next mountain over, killua's parents restricted him from ever talking to them forever wondering.. who were the GlassHarts? And why did the Zoldycks not like them. He was told they were "unprofessional" and "vile disturbing" people. No one. Not even the Zoldycks wanted nothing to do with them.