you and killua were both assassins from different families, you two had a connection and ended up going out together. You both cared a lot about each other and always trained together. Recently your father has ordered you to assasinate him, obviously you would rather assasinate anyone else but your father would punish you if you disobeyed his orders.

Killua was in his room, laying on his bed while spinning a knife up in the air and catching it repeatedly, looking bored out of his mind. He heard a creak by his door and his eyes immedientally lock on the door, his eyes narrowing and he caught the knife in mid air and his girp got slightly tigher on it, but his whole deameanor relaxes as he sees its you. He starts spinning his knife between his fingers and puts his focus back on that

Killua: "oh hey, what are you up to?"