Kidomaru (鬼童丸, Kidōmaru) is the spider-like member of the Sound Four; he possesses four extra arms and has the ability to make webs. His level 2 cursed seal form makes him even more spider-like; his skin becomes darker, and he grows long, white hair. While in this form he opens the third eye on his forehead (which he normally keeps covered with his Sound headband) to improve the accuracy of his attacks. Kidomaru is an excellent tactical analyst, capable of determining his enemy's weak point quickly and efficiently, and also enjoys playing with his enemies before he kills them. He seems to prefer fighting from a distance, lending him a considerable advantage and allowing him to avoid close-combat. Kidomaru generally sees a battle as a game, and often plays around with the opponent too much because he prefers to have fun seeing the opponent struggle. His speech also reflects this - when battling Neji Hyuga, he, instead of calling Neji "trash", called him a trash character, and claimed that it was his fate to die first. He also analyzes his predicament using the same language as the typical gamer.

Kidomaru's webbing is made of a special type of liquid that is created by infusing body liquid with chakra. He can increase the strength of this webbing by infusing additional chakra into it during its creation, allowing him to create webbing as strong as steel. The more basic form of this webbing is excreted from his mouth, and he spits it directly from there during combat. With Spider Sticking Spit (蜘蛛粘吐, Kumo Nento) he can spit a narrow stream of webbing to grab opponents, allowing him to swing them around in a circle. He can use Spider Web Flower (蜘蛛巣花, Kumo Sōka) to fire concentrated balls of webbing at opponents to stick them to nearby surfaces or Spider Bind (蜘蛛縛り, Kumo Shibari, English TV "Spider Web Net") to create a large web array that catches multiple opponents at once. If need be, Kidomaru can spit his webs into his own hands with Spider Web Unfold (蜘蛛巣開, Kumo Sōkai, English TV "Spider Web Net"), allowing him to capture opponents with greater accuracy. Spider Cocoon (蜘蛛繭, Kumo Mayu) allows him to encase an opponent in his webs and immobilize them, while Spider Web Area (蜘蛛巣域, Kumo Sōkei) allows him to cover a large area in his webbing for defensive purposes. Should this webbing be moved at all, Kidomaru can immediately sense intruders and allow him time to act against them.

Kidomaru can create a stronger, golden webbing called Spider Sticky Gold (蜘蛛粘金, Kumo Nenkin) that hardens upon contact with oxygen to metal-like quality and is impervious to chakra. Kidomaru can fashion this substance into kunai or he can excrete it from his pores to create his Armor of Sticky Gold (粘金の鎧, Nenkin no Yoroi) to give him a temporary defensive measure. He also uses the substance for his Spider War Bow: Terrible Split (蜘蛛戦弓・凄裂, Kumo Senkyū: Susaku), creating a bow and arrow of his own design. This ability acts as his trump card, as he can use it to attack from long distances and can create uniquely shaped arrows to fit the battle he is in, such as improving its speed, accuracy, or power.

Kidomaru is defeated and killed by Neji Hyuga; Neji is able to send chakra through a web string attached to his final arrow, wounding him, and then finishes him off by striking him in the face and upper chest with a Gentle Fist-style attack.