Sound Four

The Sound Four were Orochimaru's elite bodyguards, though they are technically five despite Sakon and Ukon counting as one entity because of their their kekkei genkai. Seeing their opponents as inferior to themselves, each member was given a cursed seal. The four were reluctantly forced to accept Kimimaro in their ranks when he single handily defeated them all, their group temporary called the Sound Five until Kimimaro's illness kept him from participating normally as the Sound Four supported Orochimaru during the Invasion of Konoha.

When Orochimaru sent the Sound Four to bring him Sasuke Uchiha, 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 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 he joined the fray to ensure the mission succeeds, Kimimaro 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.

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 destroy it. Denied their revenge, the Sound Four attack Naruto before he easily defeats them as they are sent back to the afterlife.

Abilities
Despite being young, all four of them are strong enough to become Orochimaru's bodyguards, and were all talented with barrier and sealing techniques. In the anime, Shikamaru stated that each members' prowess was of jōnin-level. Shortly after their introduction during the invasion of Konoha, they used Four Violet Flames Formation to create a box-like barrier, that causes anything that touches it to burst into flames. When the group later fetched Sasuke, they used the Four Black Fogs Formation and Dark Sealing Method to protect Sasuke from harm. As the group later rested, they set up a Barrier Method Formation. Each member of the Sound Four also had a cardinal direction associated with them; this was probably a reference to their positions when performing techniques as a group: Jirōbō of the South, Kidōmaru of the East, Sakon and Ukon of the West, and Tayuya of the North. In the anime, they were also capable of using the Space–Time Technique Formula: Underworld Turnover.

As with most of his powerful followers, Orochimaru branded them with different cursed seals, which greatly enhanced their individual abilities.

Trivia

 * The recurring symbol on the Sound Four's tunics was the yin-yang, though the yin colour (black) was missing. The missing yin represented imbalance, alluding to their evil natures and to that of the seals, preventing harmony in life.
 * Jirōbō and Sakon (and Ukon) specialised in close-quarter combat, while Kidōmaru and Tayuya specialised in long range combat. Kimimaro was balanced in both types.
 * Each member of the Sound Four tends to have a flaw in their personality that slows down the team: Jirōbō gets hungry and stays behind to feed, Kidōmaru tends to play around with his opponents if they interest him, Sakon can easily lose his temper and showcases the fact that he is the strongest of the four by not stopping until his opponents are dead, and Tayuya has a "doesn't want-to-lose" mentality.
 * Kidōmaru was the only member to wear an Oto forehead protector.
 * The Sound Four were playable characters in Naruto: Gekitō Ninja Taisen! 4, but they only appeared with the Second Stage of the Cursed Seal. Later, the Sound Four were playable characters in the Naruto: Ultimate Ninja 3, 4 and 5 with both regular and Cursed Seal forms playable.