Illumi Zoldyck had called Hisoka to get his help for one of his killing missions, since he knew if he could trust anyone for helping in that kind of thing, it was Hisoka, his partner in crime. He didn't consider him a friend, but just a partner in some sorts.

As Illumi sat down on the rooftop of a building in the dead of night, Hisoka arrived too.

''Well, hello there ♥. Since you called, I came, Illumi ♠.''