Jiraiya

Jiraiya is one of the legendary three Sannin, along with Tsunade and Orochimaru, who was trained by the Third Hokage himself. He is a self proclaimed Mega-pervert, and writes popular adult book series called Icha Icha, a favorite of Kakashi Hatake. He is also known as the Toad Hermit, because of his signature toad summonings. Jiraiya has the kanji for "oil" on his forehead protector. He was the Fourth Hokage's teacher and now is Naruto's, who calls him Ero-sennin, or Perverted Hermit or in the English anime, "Pervy Sage." He proves this in his childhood when he peeped on Tsunade in the baths, resulting in him being beaten to an inch of his life.

Despite his pervertedness, Jiraiya is a Kage-level ninja. During a war the team consisting of Jiraiya, Orochimaru and Tsunade came to battle "Salamander" Hanzo of the Rain village. They were defeated, but Hanzo was so impressed that they survived his attack that he gave them the title of Sannin, the legendary three ninjas (which he ordered they refer to themselves as in exchange for their lives). In his early years, Jiraya invented the Transparent Escape Technique to help him peak on women and not get caught.

Chunin Exams
Jiraiya first meets Naruto Uzumaki while he was "researching" at the hotsprings in Konoha, where he flattened Ebisu when he almost exposed him. Because he knocked out his teacher, Naruto demanded Jiraiya to train him, which he initally refused. It wasn't until Naruto used his Sexy Technique did he win Jiraiya over.

When they start training, Jiraiya removes Orchimaru's Five Element Seal off the boys stomach which allowed him to tap into the Demon Fox's chakra thus allowing him to use better jutsus and allowed him to mold his on chakra with ease. For special training for the last part of the exams Jiraiya taught Naruto how to use the Summoning Technique, but was met with very poor results. To this end, Jiraiya decided to force Naruto to use the Fox's chakra, by pushing him off a cliff. After Naruto survives this training and summons Gamabunta, Jiraiya stays in Konoha for the events to play out. When Orochimaru and the Sand attacked Konoha, Jiraiya appeared with a giant yellow toad to help battle one of the Sounds summoned snakes.

The Search for the Fifth
After the death of the Third, the village elders, Homura Mitokado and Koharu Utatane, requested that Jiraiya become the next Hokage, which he quickly turns down. Instead he volunteers to search for his former teammate Tsunade, and took Naruto with him for more training. Jiraiya would train Naruto to use his fathers technique, the Rasengan, a jutsu more powerful than Chidori.

Before they could reach Tsunade, Orochimaru contacted her in an effort to have his dead arms fixed by Tsunade's medical jutsu. Tsunade, deciding to meet Orochimaru herself, drugs Jiraiya's sake and heads out on her own. When Jiraiya, Naruto, and Shizune catch up with her, she is already in battle with Kabuto. Jiraiya goes into battle with Orochimaru, trapping Orochimaru's snake with his Underworld Swamp jutsu. Although the weakened jutsu fails to envelop the snake completely, it is still more than large enough to immobilize it. After Naruto takes Kabuto out of battle with a now-perfect Rasengan (made with the help of a clone, an innovation he came up with mid-battle), Tsunade joins Jiraiya in the battle against Orochimaru. With their ultimate summons, Gamabunta and Katsuyu, the two take on Orochimaru and his snake Manda. The healthy Tsunade proves too much for Orochimaru and Manda, defeating the two and causing them to flee. With Tsunade now accepting her post as the Fifth Hokage, they return to Konoha.

Sasuke Retrieval
Jiraiya wasn't in Konoha during Sasuke's defection and reappears only after Naruto returns after failing to bring him back. Jiraiya reveals that Sasuke and Orochimaru are very similar, in that both only lust for power and both will do anything to get it. In fact, Naruto's battle with Sasuke was very similar to Jiraiya's fight with Orochimaru when he tried to bring Orochimaru back, trying to remind his friend of their past friendship. When Jiraiya called Naruto a fool for even considering trying to rescue a friend like that, Naruto tells him he would rather be a fool than to give up on Sasuke. Taken aback, Jiraiya tells him that once he is better, he will take him to train for three years so he will be strong enough to bring Sasuke back, and protect himself from the Akatsuki.

Part II
After taking Naruto back to Konoha, Jiraiya goes off to search for info on the Akatsuki. Jiraiya would reappear later to inform an injured Kakashi and inform the current leader of Team 7, Yamato about Naruto's four tail transformation, a form so powerful that it nearly killed Jiraiya before he stopped it. It is later revealed that Jiraiya himself released it (not expecting Naruto's loss of control) with a special key passed down from the Fourth Hokage, capable of unlocking Naruto's seal. Jiraiya appears again to inform Naruto and Sakura that Sasuke has killed Orochimaru and is most likely going off the kill Itachi, before doing more research on the Akatsuki.

Jiraiya later returns to Konoha once more to inform Tsunade that he has found the location of the Akatsuki Leader, somewhere in Amegakure. After a chat with Tsunade revealing much of Naruto's history, he heads out to the Rain country. He infiltrates the village using a particular frog with a jutsu that warps in size and begins interrogating two ninja he abducted in that same frog. There is no initial response, but he is immediately spotted by Pein's rain jutsu. Upon learning that Pein singlehandedly defeated Hanzo, he summons the frog containing the key to Naruto's seal, and informs it to go to Naruto if he dies. Rather than wait for Pein to come to him, Jiraiya prepares to do battle (to forcibly extract the information).