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; due to this, he tends to slow down his team by playing too much with an opponent he is interested in. His speech also reflected this when battling Neji Hyūga, he referred to Neji as a "minor character" and analysed his situation using typical gaming language ("level" and "difficulty"). Like the other members of the Sound Four, he is extremely arrogant with his opponents. Kidōmaru was also the only member of the Sound Four not to have a perception of morality.

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 dark red, he gained horns on his forehead, shoulders and elbows, grew long white hair, and gained spinnerets enabling him to spin webs without using his chakra. Kidōmaru was an excellent tactical analyser, 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 armour 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. He could also make the Kyodaigumo to burst into his thread for aid in battle.

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. Kidōmaru used his Spider Bind technique to prevent Konoha ANBU from following them.

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 after having left Chōji behind to deal with Jirōbō, Kidōmaru allowed his comrades to go ahead of him while he caught and toyed with their pursuers. Because Naruto could use shadow clones, Kidomaru decided to kill him first. Kidōmaru slowly picked the clones off to try and find the real one. When all turned out to be shadow clones, the real Naruto attacked Kidōmaru from behind. He dodged and caught Naruto and tried to kill him but is stopped by Neji, who freed him having already freed everyone else 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 sent several volleys of webs at Neji and managed to pin him to a tree, but Neji broke free and even managed to get close to and attack Kidōmaru with his Eight Trigrams Sixty-Four Palms, though Kidōmaru blocked it with his armour. Since he couldn't win a close-range battle, Kidōmaru fell back and attacked Neji at a distance. Neji's Byakugan allowed him to detect all incoming attacks, which he blocks with his Eight Trigrams Palms Revolving Heaven and then threw a kunai at Kidōmaru which he barely dodged. Finally viewing Neji as a challenge, Kidōmaru activated the first stage of his cursed seal.

He then summoned the Kyodaigumo to blanket Neji in webbing and prevent him from using his Eight Trigrams Palms Revolving Heaven technique against his attack, but Neji is still able to dodge by slowing it down with chakra. Kidōmaru then continued to attack Neji by sending more spiders and kunai at him. He noticed that Neji did not avoid all of his attacks when a kunai cuts Neji's shoulder, and upon further testing realised the Byakugan had a blind spot. He then sent more kunai and spiders and hits him twice more. He claimed he couldn't beat him before signalling the Kyodaigumo to finish Neji. Neji repelled it with his Gentle Fist only for it to turn into thread. Kidōmaru then attacked Neji with more kunai and hit him three more times causing him to collapse. Kidōmaru then stated he had enjoyed himself even though he knew he would win before starting to leave. At that moment, Neji stood up again.

Happy that Neji had been so much of a challenge, Kidōmaru advanced to his cursed seal's second stage and created a bow and arrow. He fired at Neji's blind spot, but Neji is able to move it in time to keep it from hitting a vital organ and instead it hits him through his shoulder. Surprised, Kidōmaru realised that Neji must have been using exuded chakra to sense attacks directed at his blind spot. 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 will hit Neji, but it was thrown off by the trees. Kidōmaru then jumped to the top of the tree line for a better vantage point and created a new arrow with spin so it will cut through a tree if it hits one. He then attaches a thread to ensure that he will hit Neji that time. He succeeded, but Neji - seeing the cord - sent some of his chakra through it back to Kidōmaru, damaging several of his internal organs causing him to fall. Kidōmaru could still move though and became angry with himself for getting damaged in such a way.

Kidōmaru however believed this to have been Neji's dying effort and started to leave, all the while Neji was locating and approaching him. When he got close enough, he found he was wrong about Neji when he jumped up and turned off his chakra with his Gentle Fist attack and delivered a fatal blow to Kidōmaru's heart, causing him to scream in agony and collapse to the ground. Kidōmaru then returned to his normal form having lost all his chakra and asked Neji how he was still alive. Neji told him he couldn't let down his friends while also telling him that he was the strongest opponent he had ever fought.

As he coughed up blood and started dying, Kidōmaru told him that there is no way to save Sasuke since he had come voluntarily. Kidōmaru then collapsed again saying he hadn't been pushed that far since Kimimaro. With his last breath, Kidōmaru cursed Neji then died, leaving Neji the victor of their battle.

Trivia

 * He was the only member of the Sound Four to be seen wearing an 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 favourite 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!"