Board Thread:Questions and Answers/@comment-25951143-20150101110046/@comment-3229139-20160322065934

I also feel that Alluka is a girl and Nanika is a boy, their personalities are pretty different...Alluka is joyable and active, she used to call Killua as "onii-chan", but Nanika is calm and silent, he used to answer "'kay" instead of talking much, and also refer Killua as "Killua". Nanika means something, but the written Japanese is 闇 (yami) but not 何か (nanika), "yami" means "darkness" and it probably has some connection to the Dark Continent. So for me it's like two different souls using one body LOL.