Sound Five

To keep Otogakure's echo loud and clear, for all to hear. This is the purpose of the Sound Five (音隠れの忍五人衆, Otogakure no Shinobi Gonin Shū, Literally meaning: Hidden Sound Shinobi Five People). Originally bodyguards to Orochimaru, they play a bigger role in the post-Fourth War timeline after the creation of Otogakure in the Land of Sound as an official village.

First Generation
Despite their young age, all members of the Sound Four were among Orochimaru's strongest ninja and become his personal bodyguards. In the anime, they were originally Orochimaru's captured experiment subjects, and after being pitted against other prisoners in a death brawl and surviving via desire to live, they were granted the positions of Orochimaru's bodyguards.

The strongest among them was Kimimaro, who was one of Orochimaru's most prized subordinate, possessing the rare kekkei genkai Shikotsumyaku of the Kaguya Clan and a candidate to be one a host body for their master. After a young Kimimaro befriended Jūgo and brought him to Orochimaru, the Sannin learned of senjutsu and master it at Ryūchi Cave. Unable to use Sage Mode properly, Orochimaru instead devised the cursed seals by combining his senjutsu chakra into the mutative enzymes he isolated from Jūgo's blood. After testing his juinjutsu on several subjects, Orochimaru placed the finalised versions on the Sound Four to increased their strength.

Sometime later, Kimimaro was branded with one of Orochimaru's strongest cursed seals, the Cursed Seal of Earth, and then fought the Sound Four to test his new powers. After defeating the Sound Four with ease and leaving a rather fearful and negative impression on them, Kimimaro become the group's leader before stepping down due to his terminal illness. In the anime, Kimimaro and Sound Four was revealed to have participated in the killing of and his team so that Orochimaru could impersonate him and infiltrate the Chūnin Exams, with the members likely posing as Shiore's team-mates as well.

After assassinating of the Fourth Kazekage and his bodyguards, Orochimaru and the Sound Four masqueraded as them in perpetration to invade Konohagakure, whilst Kimimaro's disease fully manifests and was send back to Otogakure to be (unsuccessfully) treated by Kabuto Yakushi. Once the Konoha Crush began, the Sound Four discarded their disguises alongside their master and erected the Four Violet Flames Formation barrier to prevented anyone from interfering in the battle between Orochimaru and The Third Hokage, Hiruzen Sarutobi. After his defeat, they carried Orochimaru out of the village and retreated back to Otogakure.

When Orochimaru sent the Sound Four to bring him Sasuke Uchiha, they are soon confronted and entered multiple battles within the three-day limited time of their mission. After exerting themselves against two Konoha Jonin, Jirōbō and Kidōmaru were respectively killed by Chōji Akimichi and Neji Hyūga when they and their team were deployed to bring Sasuke back to Konoha. Sakon and his brother Ukon overwhelmed Kiba Inuzuka while Tayuya almost killed Shikamaru before the remaining Oto ninja were killed off when their opponents received aid from Kankurō and Temari. Though Kimimaro later joined the fray to ensure the mission succeeds (which did, as without him the opposing team would have retrieved Sasuke), he died from his illness as he almost killed Rock Lee and Gaara.

It would be revealed years later during the Fourth Shinobi World War that Kabuto Yakushi assimilated DNA samples from the Sound Four and Kimimaro, using Sakon and Ukon's Attack of the Twin Demons ability to create a shape-shifting construct from his body to use the abilities of the entire Sound Five. Kimimaro himself was brought to life with Summoning: Impure World Reincarnation to assisted in the war, believing Orochimaru was the one who summoned him, and fought diligently until his soul was released back to the afterlife.

In the anime, the Sound Four are reincarnated by Kabuto as a part of a "wish granted" by Orochimaru, from a promise that they would become "the ones who seek vengeance" after their deaths. Kabuto took advantage of this not only for them to serve as test subjects on how the cursed seals function with reincarnated ninja, but also as a diversion to slow down the remaining Allied Shinobi Forces while he prepared his trump card. Believing they were all brought back by Orochimaru as a reward, the Sound Four engaged their respective Sasuke Retrieval Team opponents in battle again. Though their opponents got stronger since the last time they fought, the Sound Four trapped them with the Space–Time Technique Formula: Underworld Turnover technique so they can have their revenge even if they are somehow defeated. However, Shikamaru tricks the Sound Four into embracing their undying hatred so Naruto can find the barrier and it. Denied their revenge, the Sound Four attack Naruto before he easily defeats them as they are sent back to the afterlife.