Pain is the recognized leader of Akatsuki, partnered to Konan, with Tobi acting as his benefactor. He is the principal figure in the tailed beast sealing ceremony.
The first and leading "Pain" appearing in the series is actually Yahiko, one of six animated corpses collectively known as "The Six Paths of Pain" that are all controlled by one person's will[ch. 378, 419]: Nagato of Amegakure. At a young age, Nagato was secretly visited by Madara Uchiha who implanted his Rinnegan (lit. "Saṃsāra Eye") into the child's body, giving him the ability to use abilities based on the six Buddhist paths of reincarnation. Orphaned, Nagato met fellow orphans Konan and Yahiko before they are all trained by Jiraiya. Nagato desired peace for the world, aiding Yahiko to create the Akatsuki to achieve that shared dream. However, a trap laid by Amegakure's dictator Hanzo led to Yahiko's death, causing Nagato to take over as the new leader of the organization. Though the encounter crippled Nagato, the experience of having his best friend die caused Nagato to come to the realization that peace could only be attained by teaching the world the pain caused by war. To that end he adopted the alias "Pain" to conquer Amegakure and invented the Six Path of Pain to overcome his handicap and kill Hanzo, becoming a "god" in the eyes of Amegakure's citizens. Having made cosmetically alterations to the other Paths by dying their hair to match Yahiko's, the Paths are all outfitted with a number of body piercings that serve as a means for Nagato to control them and to give them a "more dangerous" appearance in relation to their name's installation. Through Nagato's Rinnegan, they can also share visual information and coordinate attacks. Jiraiya would later confront Nagato regarding his role as "Pain", the leader of Akatsuki. The two would fight with Nagato dismissing his former mentor's ideals as well as killing him. During Pain's attack on Konoha, the six Paths are defeated by Naruto. Talking with Naruto, Nagato renews his faith in his late master and in the possibility of peace. Nagato sacrifices his life in order to revive the people he killed in Konoha.[ch. 449] Nagato is later resurrected by Kabuto and sent alongside Itachi to battle Naruto and Killer Bee, but is sent back to the afterlife.(Source: Wikipedia)