Yahiko

was a shinobi from Amegakure. His body acted as the Deva path of Nagato's Six Paths of Pain.

Background
Yahiko was orphaned during the Second Great Shinobi World War, and, thus, he started fending for himself, stealing food from others. He later encountered Konan, also an orphan, and the two began to work together to survive. After this, Konan brought another orphan, Nagato, and his dog, Chibi, into the group. At first, Yahiko was upset that she was bringing more people, but he later accepted Nagato and Chibi into his gang. Angered by how unfair the world was to them, Yahiko declared he would become a god to end the fighting.

The three eventually encountered Jiraiya, who looked after them and taught them basic ninjutsu. At one point, Nagato saved Yahiko after an Iwagakure Chunin attacked them. Afterwards, Yahiko vowed to become strong enough to protect Konan, Nagato, and eventually all of Amegakure.

Some time after Jiraiya's departure from Amegakure, the three gained a reputation as a talented shinobi team. Still desiring to create a world of peace, Yahiko and his friends went on to become fully fledged Ame ninjas, and gathered many supporters who shared their hope for a better world. Together, they began spreading their beliefs to stop war without violence. Unfortunately, the current leader of Amegakure, Hanzo, viewed Yahiko and his supporters as a threat to his power.

Working with Danzo, they captured Konan and forced Nagato to choose between either saving Konan and killing Yahiko, or not saving Konan and not killing Yahiko. Without hesitation, Yahiko drove himself into a kunai that Nagato was holding. With his final breath, he told Nagato to continue their mission of finding peace.

Deva path
Nagato, using his Rinnegan and chakra receivers, incorporated Yahiko's body into his Six Paths of Pain jutsu. As the Deva path, Yahiko's body had acted as Pain's main body, it being the one he most commonly used and spoke through. The Deva path was held in higher regard during combat, some of the other bodies being sacrificed to ensure its survival. Following the Deva path's defeat and Nagato's death, Konan took both of their bodies back to Amegakure.

Personality
Yahiko's personality was similar to Naruto's. His dream was to be a leader of his village, and he never gave up no matter what. When he was alive, Yahiko had a strong "eye for an eye" philosophy. He hated the way Amegakure was looked at by the rest of the world, and hated what it had become. He was defensive of the village, saying that it was his dream to stop the endless rain, which he compared to tears, and protect the nation's citizens. Yahiko wanted to become the ruler of the world so there wouldn't be any more wars. Many of these traits were adopted by Nagato after Yahiko's death.

Among the three Ame Orphans, Yahiko seemed to act as the leader of the group. It was Yahiko who first approached the Sannin to ask for food, and was the first to ask Jiraiya to teach them ninjutsu. He also seemed to act as an older brother for Nagato, reminding him to not cry and to act more manly. He also wished to become stronger so as to protect Nagato and Konan.

Abilities
Yahiko had the ability to use water-based jutsu, although the only example of this shown in the series was Water Release: Violent Water Wave, in which he was able to shoot a jet of water from his mouth. The Deva path also had the ability to control rain, presumably Nagato fulfilling Yahiko's desire of "stopping the endless tears".

Trivia

 * Yahiko shared his birthday and blood type with his former teammate, Konan.
 * Yahiko's eyes are shown to be a light blue in the manga. In the anime, his eyes are depicted as a brown.
 * During chapter 438, when Deva Path's cloth was torn apart, there is a faint sign of stabbed wound on his stomach, likely, it's where Yahiko stabbed himself with Nagato's kunai.

Quotes

 * (To Jiraiya) "If we're gonna "understand" each other, first we gotta make 'em suffer like we're sufferin'!"
 * (To Nagato) "I'm gonna rule the world!!"
 * (Thinking outloud) "If war is going to continue-- I will become the God of the world!!"
 * (Final Words) "You and Konan... You've gotta stay alive somehow... You... are... the Messiah... You... can... really--"