Tobirama Senju

, the, was the younger brother of Hashirama Senju (the First Hokage) and the granduncle of Tsunade (the Fifth Hokage) and Nawaki.

Background
Tobirama was a member of the Senju clan along with his leader and brother the First Hokage, Hashirama. When, decades before the start of the series, Hashirama struck a peace treaty with Madara Uchiha, Tobirama helped them to found Konoha. When the First died, Tobirama was appointed as the Second Hokage. He was responsible for establishing Konoha's organizational system by setting up various organizations, such as the Academy, the ANBU, the Chūnin Exams and the Konoha Military Police Force which he created as a sign of trust towards the Uchiha clan. However, according to Madara, the Military Police was actually established to distance the Uchiha from the government of the village and place the clan under a tight surveillance under the ANBU.

Tobirama trained a three-man team of his own, Team Tobirama, which consisted of Hiruzen Sarutobi, Homura Mitokado, and Koharu Utatane. During a mission in the First Great Shinobi World War that Team Tobirama performed with Danzō Shimura, Kagami Uchiha and Torifu Akimichi, they found themselves surrounded by twenty elite Cloud ninja, known as the Kinkaku Force. Tobirama, then realized that the only way any of them could escape alive was for one of them to be a decoy and sacrifice themself; therefore having faith that he had trained his students well, he chose to sacrifice himself after he selected his prized student Hiruzen for the position of Third Hokage. Homura and Koharu would become Hiruzen's advisors. After giving the title of Hokage to Hiruzen, Tobirama went off to fight the enemies where he died a noble death in battle.

Personality
From what has been seen of Tobirama, he had pride in his abilities involving water jutsu. He also had a sense of humor, even under stressful situations. Like his brother, Tobirama felt a great deal of loyalty to the village, and placed its well-being above his own.

Appearance
Tobirama was characterized by his blue armor, white shaggy hair, red eyes and his red streaks under his eyes and on his chin. His Forehead Protector is somewhat similar to Yamato's.

Abilities
According to a young Danzō, Tobirama was the most powerful shinobi in Konoha during his time.

Water Release
Tobirama was primarily known for his mastery of Water Release jutsu, being able to make use of powerful water style jutsu in areas where there were no bodies of water. He could manipulate it to form projectiles or tentacles, and could even perform the Water Release: Water Dragon Bullet Technique with only one hand seal (use of the jutsu normally requiring 44 hand seals).

Swordsmanship & Physical Ability
In the anime, it was said that he wielded the Sword of the Thunder God, a blade with electrical abilities, and was said to have mastered its use despite the lethality. He is also shown to have great physical prowess and a considerable amount of skill in the area of taijutsu, as well as good teamwork with his older brother, Hashirama Senju.

Kinjutsu
According to Kabuto Yakushi, Tobirama is also one of the three people capable of using the Summoning: Impure World Resurrection (and most likely, he was the one who invented the jutsu).

Invasion of Konoha arc
Both he and Hashirama were revived from the dead by Orochimaru, using Impure World Resurrection, to fight Hiruzen during the invasion of Konoha. While fully aware of what was going on, and saddened that he would have to fight his former student, Orochimaru employed a special seal into the back of their heads to rob Tobirama and his brother of their free will. Hiruzen quickly resolved to kill his masters and used a very powerful fire technique that was easily counted by one of Tobirama's walls of water that was then turned into an attack that was stopped by Hiruzen's own earth wall.

During the battle, he demonstrated great teamwork and combination attacks with his brother, forcing Hiruzen to summon Enma for assistance. Hiruzen was however in his old age unable to defeat the two Hokage, as any damage that was done was simply regenerated and was further inhibited by his desire to not hurt either. His soul along with his brother's were eventually sealed by Hiruzen when he combined the Dead Demon Consuming Seal and the Shadow Clone Technique to strike both of them at the same time. Before his soul was completely removed, he and his brother apologized to their former student for the trouble they had caused.

Trivia

 * Tobirama is the brother of the First Hokage, trained the Third Hokage, and is the granduncle of the Fifth Hokage.
 * Tobirama is known as the greatest water manipulator that ever existed.
 * Tobirama is a playable character in the Naruto: Ultimate Ninja series and in Shinobi Retsuden III
 * Tobirama, along with Hashirama, Minato and the leaf village symbol, had his face appear in the ending omake of Shippūden episode 129 within the fireworks.

Quotes

 * "''Do you hear? Guide the people, and believe in them, for it's from among them that one will come who will carry on when your time is done."