Alluka Zoldyck's gender is absolutely debated in the Japanese community as well. TL from Pixiv
Although Alluka has the appearance and personality of a young girl, their gender is referred to inconsistently as described below, and since there is no depiction that definitely describes them as male or female, fans are still divided after their appearance in the work. As with other gender-ambiguous characters such as Neferpitou and Kalluto, fans have come up with various theories, including "Alluka is female, but Nanika is male", "Alluka's birth sex is male, but Killua alone treats them as female", and "The Zoldyck family raises all of their children as sons regardless of birth sex".
Examples in the work:
- In Chapter 39, the bus guide introduces them as "five siblings" [兄弟]. (If taken based on appearance, there would be three older brothers and two younger sisters, so it wouldn't be a problem to use "brothers and sisters" [兄妹].)
- In the Hunter's Guide released on 2004/6/9, they are introduced as "Killua's younger brother" (page 39). (However, the Hunter's Guide has numerous errors, including Milluki's age and Nobunaga's birthday, so it is not a fully credible source.)
- Servants call them "young master" [坊ちゃん, masculine], Illumi and Milluki use "younger brother", and Killua uses "younger sister".
- Chapter 322's title is "Brother and Sister".
- In Chapter 324, Killua calls them "a girl". (However, "a girl" is in quotation marks, and there is room for interpretation on what these marks mean.)
- Chapter 327 reveals that Alluka's personal pronoun is "atashi".
- In Chapter 328, Killua describes Alluka to Morel as his "younger brother" during a phone call.
- In Chapter 338, Killua introduces Alluka to Gon as his "little sister".
Examples from third-party content:
- In the Jump crossover game Jumputi Heroes, Killua has the line "So you've got a little sister too. Let's get along as big brothers." (This is a line he says to Hiei; Hiei's younger sister is Yukina.)
Alluka is extremely rarely used for trap fetishism. Ever since this became a subject of (bad) mass editing, there have been exactly two posts where Alluka is explicitly drawn as male, which are variants of each other. This is outnumbered by posts where Alluka is explicitly a cis female, SFW posts where Alluka is a (cis or trans) girl, and just SFW posts in general.