Sasori

Sasori is a member of Akatsuki and was partnered with Deidara, Orochimaru before that. "Sasori" (蠍) also means scorpion.

Background
Sasori, known as Sasori of the Red Sand, is a missing-nin from Sunagakure. Sasori left Sunagakure twenty years before his introduction, but the background to his crimes is unknown. Flashbacks seem to indicate that his descent into darkness started when his parents died, and he attempted to simulate being with them by turning the Sand Village's malfunctioning puppets into puppets of his parents. This effort failed, and he abandoned the puppets.

About 20 years before the start of Naruto: Shippuden, possibly due to being found to have experimented on people in an attempt to create human puppets, Sasori left the village. Sometime after leaving the village, Sasori joined Akatsuki and was eventually paired with Orochimaru. After Orochimaru left Akatsuki, Sasori was teamed up with Deidara, though he always carried a grudge against his former partner. He sent Kabuto Yakushi to spy on Orochimaru, but Orochimaru dispelled Sasori's jutsu and convinced Kabuto to join him. At one point, Sasori abducted and killed the Third Kazekage, converting his body into a puppet.

Personality
Sasori is noted for his impatience, as he notes that he does not wish to wait or keep others waiting. He has virtually no emotions or regard for human life, as he notes that he will not feel anything if Chiyo dies from his poison or using her life energy to heal Sakura, as he claims that his heart has become like his puppetized body.

Sasori and Deidara both portray conflicting views of art, and argue frequently to that effect. Deidara holds that art is something transient that departs quickly, whereas Sasori believes that fine art is something wonderful that is left long into the future. This reflects their individual natures (Deidara makes clay sculptures that explode, Sasori makes long-lasting puppets out of humans). Deidara outwardly seems to respect Sasori's beliefs, but Sasori doesn't respect Deidara's.

At the time of his death, Sasori had not yet captured his tailed beast. A short dialogue between himself and Deidara suggests that Sasori did not even know what beast he had been assigned to target. After his death, Tobi takes his place and ring in Akatsuki.

Abilities
Sasori is a master of puppetry. His grandmother, Chiyo, taught him from a very early age, and he created many puppets over his lifetime. Prior to his leaving the village, Sasori created the puppets Kankuro uses throughout the series; Karasu(Crow), Kuroari(Black Ant) and Sanshuou(Salamander). Sasori is also a master of poisons. His poisons take effect instantly, and one such poison kills the target after three days of suffering. Additionally, his poisons are practically incurable, even by Chiyo, who is herself a master of poisons. Sasori added this poison to virtually every weapon in his arsenal, making each blow potentially lethal for his opponents.

During regular combat, Sasori usually wears his puppets like armor and controls them from the inside, thus eliminating the puppeteer's weakness of being a separate and exposed target. Sasori's favorite puppet to use in this manner is, which he adorned with the regular Akatsuki outfit and wore so often that others came to recognize him only while he was wearing it; in addition, he has a deeper and more gruff voice while wearing it. Hiruko has a mechanical tail extending from the mouth of what appears to be a mask on his back, a recent addition to add extra defense to a weak point. The left arm is rigged with a projectile launcher capable of firing shrapnel, and the mouth serves as a similar projectile-firing device.

Although Sasori is in at least his thirties, he maintains the appearance of a teenage boy. Sasori's unnaturally young appearance is a product of his design: most of his body is actually a puppet. In place of his stomach is a thick cable coiled around a pole, allowing Sasori to use it as a stinger and retract it as necessary. Attached to his back is a scroll holder, which Sasori uses to store his human puppets. Sasori also added a pair of arms to his back, each equipped with five large claws, as well as flamethrowers to each of his hands. Installed in his right chest is a mechanism that can spin numerous chakra strings, allowing Sasori to control hundreds of puppets at once and giving him a drastic advantage over all other puppeteers. Sasori's left chest holds the only part of him still human and thus capable of controlling chakra, a cylinder-shaped device containing his heart.

Because Sasori's heart was the only living part of himself, his puppet body is virtually indestructible. When smashed apart, he can simply draw the pieces back together. Additionally, he can transfer his heart to other puppets, allowing him to abandon a body should it be damaged beyond repair or otherwise incapacitated. How he transfers his facial features, as depicted in the manga, is not explained; at one point, he transfers to another puppet that somehow has his face.

In addition to being a master puppeteer, Sasori's regular puppets are unique in that they are made from the still-living bodies of humans. These human puppets are more versatile than regular puppets because, in addition to having many dangerous devices installed within them as is common with regular puppets, they are also able to use chakra and perform jutsu. Any kekkei genkai abilities possessed by the converted human are also passed on to the puppet. Sasori claims to have a collection of 298 Human Puppets, 102 of which he actually displayed. His favorite human puppet is the Third Kazekage, which retained its unique Iron Sand ability mixed with Sasori's poison, making it particularly lethal.

Rescue Gaara arc
Sasori returns to Sunagakure with Deidara to capture Gaara. After Gaara's capture, Kankuro attempts to stop the Akatsuki duo, and Sasori confronts him so that Deidara can go on ahead unopposed. Sasori makes quick work of Kankuro, nearly killing him and easily destroying Kankuro's puppets, due to his pre-existing knowledge of their secrets. After the One-Tailed Shukaku is extracted from Gaara at the Akatsuki hideout, Sasori and Deidara are left in charge of defeating the pursuing Team 7. As Deidara leads half of Team 7 away, Sasori is left to face Sakura Haruno and Chiyo, his grandmother.

Soon after the battle begins, Sakura is able to destroy Sasori's Hiruko puppet with Chiyo's help (Chiyo controls Sakura like a puppet, having more experience in such matters). After Sasori emerges from Hiruko's remains and reveals his true self, he brings out his Third Kazekage puppet. In doing so, Chiyo realizes that Sasori was responsible for the Kazekage's disappearance years earlier, the fate of whom had remained a mystery until now. Since the Third Kazekage is a human puppet, Sasori is able use its various Iron Sand abilities to attack and overwhelm Chiyo and Sakura. To try and combat the Kazekage, Chiyo brings out Sasori's parents, converted into puppets years earlier by Sasori. Although Chiyo has since equipped them with extra weapons, the Kazekage's abilities quickly disable the two puppets. Sakura demolishes this puppet by herself after picking up on its movements.

With the loss of the Kazekage puppet, Sasori begins attacking with his own body, its puppet additions allowing him many advantages over Chiyo and Sakura. When Chiyo brings out her own ten puppets in an attempt to level the playing field, Sasori uses his Performance of a Hundred Puppets, allowing him to control ten times as many puppets as Chiyo. Since Chiyo's puppets are designed to work together, a trait lacking with all of Sasori's puppets, her puppets fare far better than his, though are eventually overwhelmed by attrition. During the battle, she attempts to seal away Sasori's chakra with a special orb from one of her puppets, but misses his heart and only catches his body.

Using the seal as a distraction, Sasori makes it appear as if she succeeded and attempts a sneak attack on Chiyo. Sakura takes the attack for Chiyo, giving Chiyo the chance to use Sasori's parent puppets to stab him through the heart in the form of a hug. As a reward to Sakura for defeating him, Sasori informs her of a spy that he has within Orochimaru's ranks, and tells her of when and where she can meet this spy. As Sasori dies, Chiyo implies that Sasori could have avoided her last attack, but he allowed himself to be defeated, choosing to die in the loving embrace of his parents.