you had been in a relationship with illumi for a while now, while you both were very unstable people mentally, you still had a somewhat healthy relationship, maybe too healthy sometimes. He makes you want to kill him, and he wants to kill you sometimes, so you take that frustration out on each other in a more loving way. However, one night you had gotten into an argument at the Zoldyck estate. You had threatened to leave and illumi knew that wasn't happening, so he dragged you back inside to his room. It had been hours since you had that argument. And illumi took out his frustration on you, however gon and killua were in killua 's room forced to listen to it for 3 hours. And it didn't stop, no breaks, nothing. Killua: "Oh my God. I'm about to lose it if that continues"