As a child from the Sand village, his parents were killed during the war between the Sand and Leaf Villages by Kakashi's father, Sakumo. After this his grandmother Chiyo took care of him, not telling him that his parents died... and he waited for them to return. Knowing of his depression, she decided to teach Sasori puppetry. His skill rapidly improved despite his young age and Chiyo allowed him to use her workshop to create his own puppets. The puppets he made were perfect copies of his parents with which he acted out daily routines with as if they were alive. He would develop a hatred of waiting and making others wait.
Twenty years before the start of the series, Sasori left the Sand Village. Before that however he became well known for his ability to create "human puppets," puppets that were made from the bodies of his enemies that he was able to preserve. What made these puppets so dangerous was not only the weapons and traps that were built into them like any other puppet, but they retained their chakra and techniques which Sasori could make use of. His most used human-puppet was Hiruko. A puppet master's weakness is that they are left vulnerable while controlling their puppets, so Sasori specifically made Hiruko as both a weapon and a suit of armor.
After he left the Sand village, he would both destroy an entire village and join the criminal organization known as the Akatsuki.
Return to the Sand/Fight Against Sakura
He would fight Kankuro, a young puppet master from the Sand village. Though Kankuro was skilled, Sasori was an expert and Kankuro succumbed to Sasori's poison after short battle. Sasori would then fight the combined might of his puppet-master grandmother and Sakura. He fought them first inside of Hiruko, and soon they realized that Sasori has a tendency to cover every edge found on his puppets' weapons with poison, making even a scratch potentially lethal. Sakura's great strength that she gained under the training of Tsunade was able to crush the Hiruko puppet, causing Sasori to find safer ground. He then not only awed his grandmother by revealing the fact that he still looks like a teenager after twenty years, but that he had the missing The Third Kazekage as his most prized human-puppet.
Despite some close calls, Sakura was able to survive most of the Kazekage's traps and poisons, at which point Chiyo summoned her puppets to help battle Sasori, the puppet replicas of Sasori's parents. They were effective for a bit and managed to remove many of the Third Kazekage's weapons and traps until Sasori started using the Third Kazekage's infamous "Iron Sand" techniques, which used to immobilize the puppets of his parents.
The iron sand would result in a lot of trouble for Sakura, especially since that too was laced in poison, but she was thankfully being partially controlled by Chiyo which allowed her to avoid things that she could not avoid on her own. After a very close call from one of the Third Kazekage's most dangerous iron sand techniques, "World Method," Sakura was able to destroy the Third Kazekage puppet and put an end to the threat of the iron sand.
Revealing a Secret
Sasori then revealed the secret to his youth, he turned almost all of himself into a human-puppet... and a very dangerous one at that, armed with built-in flamethrowers and high-pressurized water jets that were able to slice through stone. He went on to use his abdominal "tail" to injure Sakura and thrust himself towards his grandmother to kill her with his buzz saws on his back, but was stopped by Sakura's amazing strength which ultimately caused him to fall apart, but he was able to pull himself back together. Chiyo then summoned 10 puppets created by the first puppet-master, Monzaemon.
Sasori retaliated by using one of the unique modifications he was able to add to his puppet body, the ability to control 100 puppets. Unfortunately Sasori went for quantity over quality and summoned more then he could properly control, but he was able to gain more control over the remaining ones that weren't destroyed, ultimately gaining the advantage. Sakura used an item from one of Chiyo's puppets that allowed her to seal Sasori's body, making him unable to use his chakra. However Sasori was able to escape by sending the plug on his chest to another puppet.
Sasori in the new puppet body snuck up behind his grandmother and was about to kill her, but Sakura jumped in the way of the blade. Chiyo then used the opportunity to use the puppets of Sasori's parents to stab him through the plug. This plug she realized was the only part of Sasori that was alive... it was a container that held his heart. Knowing he was dying, he gave Sakura and Chiyo a reward for defeating him, knowledge on where to meet his subordinate whom he had spying on Orochimaru. Chiyo would later comment after Sasori's death that he saw her attack coming, but did nothing to avoid it.
Fourth Great Ninja War
Since then Sasori's body was found by Kankuro which he uses as his new puppet, and has been training with it to learn it's abilities. He first revealed it at the Kage summit using one of Sasori's hidden mechanics, shooting a hail of blades connected to bombs. Later revealed is a chakra shield mounted on the right arm, and the left hand can extend with a cable.
Sasori was later resurrected by Kabuto Yakushi, along with Deidara, Shin, and Chukichi to be used as an ambush squad during the Fourth Great Shinobi War. They attacked Anko's squad that they caught lurking around Tobi's lair and Sasori took control of them as his living puppets, including an Aburame after Deidara weakened them with his bombs. They then encountered the Allied Shinobi Force's ambush squad composed of Kankuro, Omoi, Sai, Ittan, Tango, Saji, Hoheto Hyuga, and Kiri. Sasori sent in the Aburame to get the drop on the squad, using his insects to jam their sensors. Saji went to help him but he told Saji to get away, as it was revealed that Deidara hid his exploding clay within the Aburame and detonated it. Kankuro managed to save Saji but not the Aburame and Ittan used an Earth jutsu to protect everyone. Sasori had the sent in the other living puppets and Omoi fought them off. Shin attacked, but Sai pounced on him and broke his neck, but it couldn't kill the undead Shin and Sai was shocked to see him.
Shin and Sai fought while Omoi went after Deidara. Sasori used his living puppets to attack Omoi, but he cut Sasori's chakra strings and Kankuro used his chakra strings to snare Sasori's own strings and pull him out of his hiding place and landed on Deidara. Sasori was impressed by Kankuro's skill, and then Kankuro revealed that he's using Sasori's old body. Sasori remarked that he now has a body that is eternal and will never rot, something what he always wanted. He took control of Shin and sent him to attack, but Kankuro fought him with Sasori's puppet body and Omoi jumped in to help. Sasori pulled Shin away and Deidara was going to activate his bomb that he put inside of Shin, but Kankuro contained Shin inside his Salamander puppet; it was destroyed and Shin regenerated. Sai then used his 3D drawings to attack Sasori and Deidara from behind and send them flying. Kankuro revealed two Black Ants and two Crows to trap them and impale them. Deidara was going to blow his way out, but Omoi stabbed him with his lightning-infused sword to stop him. Kankuro then lectured Sasori, saying that his strength came from the soul he was trying to get rid of, and that it was his heart and soul that he put into his puppets that made them lasting, and said that Sasori has now let himself become a lifeless puppet being used by someone else. As Sasori listened to this, Shin's encounter with Sai put his soul to rest and he crumbled.
Appearance & Characteristics
Sasori never looked to enthusiastic, and was not bloodthirsty like some of the members of the Akatsuki were. He took everything in a very serious manner, and did not agree with his partner, Deidara, on nearly anything. His hair was shown to be a dark red color, and his eyes looked as though he was always sleepy. However, this could easily be explained by the fact that he wasn't actually human after turning himself into his own master creation. He was obviously respected when it came to being a member of the Akatsuki itself, as none of the members ever questioned his actions when he was alive. Like the rest of the Akatsuki members, he wore the red cloud patterned cloaks that all the Akatsuki members wore. All in all, I count Sasori as being somewhat of a mixture between Gaara and Itachi as a character. Later he betrays his grandmother Chiyo and is in a battle with Sakura to save Naruto from Sasori.