There are few things in this world Kalluto craves, wants so desperately that he can feel the ache in his chest sometimes when he sees that others already have it. Few things would drive him to leave the one place he feels accepted, genuinely welcomed, loved -- in perhaps a strange, sick way. Only something this special would bring him to his sister’s side.
“I am no longer with the Phantom Troupe.”
Carefully worded; he’s not with them now.
Kalluto remembers his brother’s offer from before -- leave the Troupe. Come with him and Alluka, instead. He so desperately wants to. Although he loves Killua dearly, craves his affection, he doesn’t know that leaving the Troupe will be worth it if Alluka is there. He just wants to see what it’ll be like before he makes a final choice.
If Killua finds out he’s lying, he can go back to the Troupe. But he doesn’t know that sacrificing what fragile relationship he has with his brother is worth the trouble.