Sasori, known as Sasori of the Red Sand, was an S-rank Missing-nin from Sunagakure, and the grandson of Chiyo, one of the elders, who trained him as a puppeteer. He was the partner of Orochimaru in the criminal organization Akatsuki until the latter left, and then the partner of Deidara until he was killed.
Sasori was born in the village of Sunagakure twenty-one years before the start of the series. His childhood was marked with tragedy as, when he was five, his parents were killed in battle by Kakashi Hatake's father, Sakumo, leaving Sasori in the care of his grandmother, Chiyo. Chiyo atttempted to fill the empty void left in Sasori's life by teaching him puppetry, a tradition in their family. Sasori's talent for this became apparent quickly, and he molded two puppets in the image of his parents to try and rid himself of the lonliness that followed his parents death, but as they were not able to give him the love he longed for, Sasori lost interest in them, and they eventully fell into Chiyo's possession. As he grew older, Sasori became an esteemed craftsman, who, on top of finding ways around the weaknesses puppet masters usually have, created several ingenious puppets, like the Crow, the Salamander, and the Black Ant puppets that Kankuro, Gaara's brother, later owned as a shinobi. Sasori's puppet's relative ease in shedding the enely's blood on the battlefields during the Second Shinobi World War earned him the nickname "Sasori of the Red Sand". Sasori eventually came to found a new form of puppetry, in which he crafted puppets from the living, known as Human Puppets, which had the advantage of retaining the abilities they had in life. He made one from the body of a shinobi known as Hiruko, which Sasori could hide inside of to prevent close-range fighters from having an easy time hurting him, and which was deadly in all ways. When he was fifteen, Sasori left the village of Sunagakure and became an S-rank Missing-nin, leaving behind multiple sleeper agents in his service. He returned 10 years later and abducted the Third Kazekage, who he killed and turned into his favorite Human Puppet. Sasori eventually made a puppet in his image, which he transfered his core into to prolong his life. Sasori eventually joined the criminal organization Akatsuki, where he was first partnered with Orochimaru, who he held a mutual respect for. However, after Orochimaru left the group following his failure to steal Itachi Uchiha's body, Sasori came to hate him, and sent Kabuto Yakushi to spy on him. However, Kabuto had already been working under Orochimaru before becoming a spy for Akatsuki, and this gambit failed, though Sasori himself was never aware of this detail. He was later partnered with Deidara.
Sasori made his debut in part 2 of the series traveling to his home village of Sunagakure with his partner Deidara, where they hoped to capture the jinchuriki of Shukaku the One-Tail, Gaara. Sasori cautioned Deidara about his prepraration to fight Gaara, but the latter seemed sure he had all he needed. Using one of his sleeper agents, Yura, Sasori and Deidara infiltrate Sunagakure without trouble, but Deidara botched up the intended covert operation for Gaara's capture. After he eventually defeated and captured Gaara, Sasori was left with defeated Kankuro, Gaara's brother, which he did with ease as the latter used puppets that he created. After they got to the hideout, they and the rest of Akatsuki removed and sealed Shukaku from within Gaara, killing him. After the rescue unit for Gaara arrived, Sasori intended to capture Naruto Uzumaki, but Deidara took Gaara's body and drew him outside, alongside Kakashi Hatake, leaving Sasori to begrudgingly fight his grandmother, Chiyo, who was backed by Sakura Haruno. Sasori's Hiruko puppet proved to be dangerous, but with Chiyo's help, both her and Sakura avoided injury and Sakuro managed to destroy Hiruko. With his real body exposed, Sasori's unaged body stunned Chiyo, and he revealed his favorite Human Puppet, the Third Kazekage, which he used to engage Chiyo, who used his Mother and Father puppets against him. After the fight reached a stalemate, Sasori utilized the Third's Iron Sand, which he managed to disable Chiyo's puppets with and hinder her by disabling her puppet arm. Sakura also stated to Sasori that she would question him as to his knowledge of Orochimaru.
Chiyo, however, with Sakuro's permission, used her as a puppet against Sasori, and, having trained under the Fifth Hokage, Tsunade, she proved to be very formidable, repelling his Iron Sand attacks, which caused the cave to collapse, impressing Sasori. Sasori quickly used a much more high-scale technique, which poisoned Sakura due to the fact that Sasori soaked the Iron Sand in his special poison, as he had all his puppet weapons(he defeated Kankuro this way). Sakura, however, had managed to create an antidote for the poison while saving Kankuro's life, and injected herself with it. After she destroyed his Third Kazekage puppet, Sasori, acknowledging her skill, revealed his true body was a puppet, which he could use a weapon as well, but hadn't done so since joining Akatsuki. Despite this new action, however, Sakura and Chiyo prevailed and destroyed his body. He reformed it, and Chiyo decided to use her most powerful puppets, White Secret Technique: The Chikamatsu Collection of Ten Puppets. To counter this, Sasori used his own strongest puppets Red Secret Technique: Performance of A Hundred Puppets. With some difficulty, Chiyo and Sakura managed to overcome this technique, having most of their puppets destroyed in the process, and Sasori was semmingly defeated by Chiyo's Lion-Headed Kannon technique. However, Sasori had switched his core into another puppet and nearly struck Chiyo, who was shielded by Sakura, who was stabbed through instead. After some conversation, Sasori detached his arm, revealing a sword, but was stabbed through the heart by Chiyo using his Mother and Father puppets in the form of a hug. Chiyo revealing that was his weakness, Sasori told Sakura of what he knew of Orochimaru, telling her to think of it as a reward for defeating him, before dying. Afterwards, Chiyo stated that he died by his choice there.
Sasori was later revived by Kabuto Yakushi as a military weapon for Akatsuki's side during the Fourth Shinobi World War, alongside all his other deceased comrades. In war, Sasori was made a part of the Surprise Attack and Diversion Platoon, which was tasked with disrupting the Allied Shinobi Forces. After things go downhill for the Akatsuki's side, Sasori joined the rest of his platoon on Deidara's clay birds, where they pursued the Infiltration and Reconnaissance Party. With trouble, the group was eventually captured and Sasori manipulated Muta Aburame after Deidara planted an explosive on him, and forced him to attack the Surprise Attack Division without their knowledge, resulting in them taking a man named Zaji hostage. Though Deidara attempted to blow up their enemy, the attack was evaded and only Muta died. Sasori, controlling other captured shinobi, attempted to battle the division, but they were freed by Omoi, a student of Killer B, the Eight-Tails jinchuriki. Aferwards, Kankuro, who Sasori had previously defeated, attacked his chakra puppet strings to Sasori's and caused him to be thrown downward, sending him crashing into Deidara ina coordinated attack pattern. Praising Kankuro, Sasori stated that he had obtained an immortal body whe he saw Kankuro reveal his old one and used Shin while avoiding Kankuro's attacks, before Deidara detonated the clay with in in attempt to attack. Before the fight could progress any further, Sasori and Deidara were both struck from behind by Sai, and captured inside Kankuro's puppets. As Kankuro then revealed that his strength came from his heart and soul, which Sasori poured into his puppets, he came to accept that they and his techniques were what immortalized him and, emotionalized in the moment, trusted his Mother and Father puppets to Kankuro as his body deconstructed, sending his soul back into the afterlife.
Sasori was made very lonely by the loss of his parents, which his grandmother, Chiyo, attempted to make up for. He was also very remorseless, at least in later years, neer regretting any of the lives he took or betraying his village. Sasori had a lot of respect for art, believing it was something preserved for the future and he had no respect for his partner, Deidara's artistic point of view of what real art was. he did not get along well with any of his fellow Akatsuki, though while Orochimaru was still with them, the two shared a mutual respect due to similar views. After he left, Sasori came to hate him and sent Kabuto Yakushi to spy for him(though the latter already worked for Orochimaru). He was also quite spiteful towards his grandmother, Chiyo, after their reunion and didn't hesitate to try and kill her, which he did multiple times through their battle.
Sasori was an immensely powerful and skilled shinobi, who was able to fight and kill the Third Kazekage, known as the strongest in the history of Sunagakure, single-handedly. He was also able to outclass his grandmother, Chiyo, also a very powerful kunoichi, and her assistant, Sakura Haruno, generally controlling the pace of his battle with them and in the end only dying by his choice, as was stated by Chiyo. A master puppeteer, Sasori became well known as "Sasori of the Red Sand" for his puppets fighting abilities, which took many lives in war. Deidara, Sasori's partner, openly admitted he was the stronger of the two, despite his own great power.
Sasori's prowess as a puppeteer was easily a match for his grandmother, Chiyo, and he was able to control as many as 100 puppets at once, a feat impossible if not for his unique body; Sasori built a puppet in his image and transfered his core into it, allowing him to prolong his life and giving him immunity to age and pain. He created many esteemed puppets and was known for his love of making puppets from living people, called Human Puppets, which retained the powers they had in life, giving them a great advantage over ordinary puppets. Sasori's favorite was his Third Kazekage puppet, which had the ability to use the Iron Sand of the Kazekage, which was called the most terrorfying weapon in Sunagakure's history. Sasori was able to increase its deadly effect by coating its weapons with his special poison, which he did to all his puppets, even himself. This poison, which Sasori created with his immense understanding of medical ninjutsu, was beyond anyone in the Sunagakure, even his grandmother, and only Sakura Haruno, trained by the Fifth Hokage, Tsunade, called the best medical shinobi, was able to counter it. Sasori claimed to have more skill that anyone in his village with medical ninjutsu. When using himself, Sasori was quite dangerous, able to shoot blasts of fire and water(anime only), and weild his personal weapons with greater ease than he could his other puppets. Notably and strange, however, under the Impure World Reincarnaton technique, his powers were lessened due to having a flesh body instead of his puppet body.