Otogakure

, called Oto for short, was Orochimaru's personal village, founded for the express purpose of collecting ninja for his experiments and his quest to learn all jutsu. In actuality, Oto is not really a village, but a group of hideouts and bases scattered throughout the Land of Sound and other countries. Sound ninja use a diverse amount of jutsu, which are mostly centered around modifications and mutations Orochimaru gave them.

Three Sound ninja (Dosu Kinuta, Zaku Abumi, and Kin Tsuchi), under Orochimaru's orders, entered the Chūnin Exam with the goal of killing Sasuke Uchiha. However, Orochimaru was actually using them as test subjects for Sasuke's power after Orochimaru gave him the Cursed Seal. Later, Otogakure assisted Sunagakure in invading Konoha. With Orochimaru being sealed by Itachi Uchiha, the fate of the village is unknown.

No one knows how you could hide an entire village in see-through vibrating air molecuals.