Shodaime Hokage, the First Fire Shadow, was one of the founders of the Hidden Leaf Village with his younger brother Nidaime, the Second Hokage. He used earth-based jutsus, which helped to sprout trees from the ground during the creation of the Village.

He is also the grandfather of the Fifth Hokage, Tsunade and was a teacher to the Third Hokage, Sarutobi. In addition, a living being named Yamato has had the First's DNA implemented into him. Kakuzu, a former member of Akatsuki, also said that he once fought with the First, but he never revealed any details.  

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Nidaime Hokage, the Second Fire Shadow,  was one of the founders of the Hidden Leaf Village with his older brother Shodaime, the First Hokage. He used water-based jutsus, and helped give the Leaf Village it's lush green apperence. He is also the granduncle to the Fifth Hokage, Tsunade, and a teacher to the Third Hokage, Sarutobi.

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Sandaime Hokage, the Third Fire Shadow,  was the the student of the First and Second Hokage and a teacher to the three Legendary Sannin - Orochimaru, Jiraiya, and Tsunade (who went on to become the Fifth Hokage). In addition, the Third is the father of Asuma Sarutobi and grandfather of Konohamaru.

He was picked to be the Third by the First and Second Hokages at an early age. He became known as "The Professor" due to his vast knowledge of jutsu and was highly respected and looked up to by all the villagers. The Third always seemed to say just the right thing to make somebody feel better, and always believed the answer to solve problems was to work it out peacefully, through verbal negations.

Unfortunately, not everybody thought that way, as Orochimaru decided to invade the Leaf Village as revenge for not being picked as the Fourth Hokage (along with the goal of catching Sasuke as well). During the invasion. the Third put on a display of his high skills to protect the village and combat Orochimaru. However, due to the severe blows he took, along with his old age, he was unable to kill his former student. As a last ditch effort to at least stop Orochimaru from using any more jutsu, the Third turned Orochimaru's arms into stone as he fell to his death.

Note: The Third Hokage had retired when he picked the Fourth Hokage, but had to come out of the retirement when the Fourth died.

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Yondaime Hokage, the Fourth Fire Shadow,  was the the student of the Legendary Sannin, Jiraiya and a teacher to Kakashi, Obito, and Rin. He is also the father of Naruto Uzumaki.

The Fourth was a brave and powerful ninja who fought with the Nine-Tailed Demon Fox, which terrorized the hidden Leaf Village, shortly after he became Hokage. He sacrificed his life to stop the Nine-Tailed Fox to stop it and sealed it inside of a baby - his son, Naruto.

The Fourth is said to be the greatest ninja the Leaf Village had ever produced. He was a genius with a talent which can only be seen once in a decade, at best, with a desire to always succeed. He was the creator of the Rasengan and is also known as "Konoha's Yellow Flash" because of his unmatchable speed to attack enemies.

Note: The Third Hokage wanted to select Orochimaru to be the Fourth Hokage, however, Orochimaru's evil intentions led the Third to select this skilled ninja as the Fourth.

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Godaime Hokage, the Fifth Fire Shadow,  is more commonly known as Tsunade - one of the three Legendary Sannin. She is the current Hokage of the Leaf Village. She was the the student of the Third Hokage and a teacher to Sakura Haruno and Shizune. In addition, Tsunade was the granddaughter of the First Hokage.

Tsunade is regarded as the best medical ninja in the world and has unbelievable amounts of physical strength. She was picked by Jiraiya (and approved by the Leaf Village council) to become the Fifth Hokage, not only because of her skills as a ninja, but because of her intellectual abilities. 

At first she rejected the offer to become Hokage because she thought it was stupid since her former boyfriend and little brother both died trying to achieve this dream. But, when she met Naruto, who showed her the same passion, hard work and determination that her brother and boyfriend had shown, she became inspired and accepted the position of the 5th Hokage.