comment #54631 It's just an illusion. AFAIK he's not meant to actually turn into a girl. It's probably the same sort of jutsu as the one that made Sasuke seem dead way back when they were training with Kakashi. The jutsu whereby they appear to die but it was actually a log or something is also probably in the same category.
Naruto's "Sexy no Jutsu" is basically "Henge no Jutsu" (Transformation Technique) that about every ninja knows. The only difference is that Naruto is one of the few ninja shameless enough to transform himself into a beautiful naked girl.
Also, Henge no Jutsu is Ninjutsu, not Genjutsu.
Genjutsu, like "Magen: Narakumi no Jutsu" (Demonic Illusion: Hell Viewing Technique) that Kakashi used on Sakura affect only people's minds; all illusions that Sakura has seen was only in her mind. Since all Genjutsu exist only in affect people's own senses, they sometimes can be broken by a person simply refusing to aknowledge Genjutsu, or, lacking that, by "Genjutsu Kai" (Genjutsu Caneclling).
Illusionary Ninjutsu, like Henge no Jutsu or "Bunshin no Jutsu" (Clone Technique) directly affect surroundings, not people's mind; unlike Genjutsu, they can't be canceled with Kai or if people refuse to believe them. It is a somewhat subtle difference between Genjutsu and Illusionary Ninjutsu, but it exists.
and since Shiyuu is being a nerdy know it all, I might as well state that back then Naruto made his Henge no Justsu transformations older then him by a bit read the first chapter you will notice.
