Kidōmaru

was a member of the Sound Four and was said by Orochimaru to be the most intellectual.

Personality
Kidōmaru generally saw a battle as a game, and often played around with the opponent too much because he preferred to have fun seeing the opponent struggle. His speech also reflected this; when battling Neji Hyūga, he referred to Neji as a "minor character" and analyzed his situation using typical gaming language ("level" and "difficulty"). Like the other members of the Sound Four, he is extremely arrogant with his opponents.

Abilities
Like the rest of the Sound Four, Kidōmaru was skilled with creating barriers and seals. When in his Level 2 cursed seal form, his skin became darker, he gained horns on his forehead, shoulders and elbows, and grew long white hair. Kidōmaru was an excellent tactical analyzer, capable of figuring out his enemy's weak point quickly and efficiently, and also enjoyed playing with his enemies before he killed them.

Unique Body
Kidōmaru had a unique body structure. He possessed two extra pairs of arms, which essentially gave him a total of eight appendages, relating to his spider theme. These allowed him to add power or variety into his attacks, hold multiple tools, simultaneously perform multiple tasks, and form several hand seals at once. He could also use the multiple arms to pull his bowstring to incredible tension, drastically increasing the arrows' power.

He also possessed a third eye on his forehead, usually concealed by his forehead protector. In a serious battle, he would reveal the eye. This eye increased his perception and accuracy by a significant amount, allowing him to pinpoint the enemy's vital points with his arrow.

Spider Webs and Sticky Gold
Kidōmaru had the ability to make spider webs by infusing his spit or sweat with chakra. These threads were extremely sticky, yet durable and elastic. This is because his chakra is constantly flowing through the webs, and they cannot be cut with normal tools such as kunai. He could use them to bind, trap, or even be used for just sensing enemies. However, the Gentle Fist can cut them, as the fighting style is based on using the user's chakra to attack precise points.

He could also create a thicker golden liquid that hardened into a chakra-blocking metal on contact with air. By chewing the spider web liquid inside his mouth, he could make it more solid and gum-like, allowing him to form makeshift weapons. However, this hardened material could be instead released through the sweat pores and fabricated into a body-covering armor that could completely defend him from physical attacks, metal throwing weapons, and even chakra-based attacks, such as the Gentle Fist. Finally, he could form his especially deadly bow and arrows which could shatter trees when fired.

Summoning Technique
In keeping with his spider-theme, he could summon the Kyodaigumo, a giant spider that spawn an immense number of smaller spiders to use the Rain of Spiders technique, which created threads as powerful as Kidōmaru's own.

Invasion of Konoha Arc
Kidōmaru made his first appearance with the rest of the Sound Four, erecting a barrier to keep others from interfering in Orochimaru's fight with the Third Hokage. He and the rest of the Sound Four later escorted Orochimaru when he fled.

Sasuke Retrieval Arc
The Sound Four escorted Sasuke Uchiha when he decided to join sides with Orochimaru. After the Sasuke Retrieval Team found the Sound Four, Kidōmaru caught them in his web and told the rest of his group to go ahead of him while he caught and toyed with their pursuers. Because several of Naruto's shadow clones had been captured, Kidōmaru slowly picks the clones off to try and find the real one. All turn out to be shadow clones, the real Naruto sneaking up on Kidōmaru. He tries to attack Naruto but is stopped by Neji, who frees everyone from Kidōmaru's webbing using his Gentle Fist. Neji engaged Kidōmaru in battle after the others had gone ahead.

Kidōmaru was at first confident that he could kill Neji very quickly. He sends several volleys of webs at Neji, but Neji breaks free of all of them and even manages to attack Kidōmaru with his Eight Trigrams Sixty-Four Palms, though Kidōmaru blocks it. Since he can't win a close-range battle, Kidōmaru falls back and attacks tries to attack Neji's blindspot. Neji's Byakugan allows him to detect all incoming attacks, which he blocks with his Eight Trigrams Palms Heavenly Spin. Finally viewing Neji as a challenge, Kidōmaru activates the first stage of his cursed seal. He summoned Kyodaigumo to blanket Neji in webbing and prevent him from using his Heavenly Spin against his attacks, but Neji is still able to dodge. Kidōmaru notices that Neji does not avoid all of his attacks, and upon further testing realizes that the Byakugan has a blindspot.

Happy that Neji has been so much of a challenge, Kidōmaru advances to his cursed seal's second stage and creates a bow and arrow. He fires at Neji's blindspot, but Neji is able to move in time to keep it from hitting a vital organ. Surprised, Kidōmaru realizes that Neji must be using exuding chakra to sense attacks directed at his blindspot. Kidōmaru creates a new arrow that is connected to him by a thread, which will allow him to move the arrow mid-flight to ensure it hits Neji. He succeeds, but Neji - seeing the cord - sends some of his chakra through it back to Kidōmaru, immobilizing him. Though angry with himself for getting damaged in such a way, Kidōmaru believes this to have been Neji's dying effort. As he falls to the ground he finds he was incorrect; Neji is waiting for him and delivers several fatal blows.

As his life fades, Kidōmaru asks why Neji tries so hard to retrieve Sasuke despite all of his injuries. Neji responds that his friends are counting on him to win. With his last breath, Kidōmaru tells Neji that they are wasting their time since Sasuke voluntarily joined them. He dies, reflecting on the fact that Neji was the strongest opponent he had ever faced since Kimimaro.

Trivia

 * He was the only member of the Sound Four to be seen wearing a Otogakure forehead protector.
 * means "demon child", and is a common ending for male Japanese names.
 * Kidōmaru can be seen during the omake of Naruto Shippūden episode 129. He's picking masks with Sakon nearby.
 * According to the Naruto Official Databook:
 * His favorite phrase is: "Game Over".
 * Kidōmaru has completed 46 official missions in total: 20 D-rank, 15 C-rank, 8 B-rank, 2 A-rank, 1 S-rank.

Quotes

 * "This game has a higher difficulty level than I thought!"
 * "I guess it was more fun this way... but now game over!!"
 * "What kind of a freak is this guy?"
 * "The weakest one in the game always goes down first!"