>>3193151Nanachi has all but been outright confirmed as a girl.
>Female in all the official concept-art for Made in Abyss' creation>Female appearance>Female voice-actress>Outright referred to as "she" in multiple translationsAkihito Tsukushi has tried to be catty about it on Twitter when asked for confirmation, simply because it makes the character more mysterious and foreign if they're an "it" rather than a "he" or "she". However, this was clearly an afterthought. The ambiguousness was only brought in after the fact when it was realized it could be used as a part of the narrative's intrigue, and that it TECHNICALLY hadn't been confirmed in the media that had been released up until that point.
Naturally, idiots and SJW's latched onto this, claiming that Nanachi is "gender non-binary" or "trans-identifying" or God knows what else, and how super-important this is because they're supposedly getting "representation" in modern anime.
The cancer that can be found in places like the Made In Abyss Wiki is testament to this.
tl;dr, Nanachi is and was intended to be female, and pretty much everybody knows it.
Tsukushi may have intended it to be ambiguous to keep the audience intrigued, but even if that's the case he clearly didn't do it with the Tumblr intentions that American audiences have projected onto it.