Tsunade

is the last known living member of the Senju Clan, and the Fifth and present Hokage of Konohagakure. She took over after Hiruzen Sarutobi died. Along with Orochimaru and Jiraiya, she is one of the Legendary Sannin of Konoha, and currently the only one still alive after Jiraiya's death and Orochimaru permanently sealed. She excels in medical ninjutsu.

Background
Tsunade is a former student of the Third Hokage. Tsunade and her former teammates, Jiraiya and Orochimaru, are known as the or simply the "Sannin". The word is often attached to Tsunade's name because she is the granddaughter of the First Hokage and the grandniece of the Second Hokage. Tsunade is well known for her extremely large breasts (106 centimeters as stated by Jiraiya), despite the fact that Jiraiya referred to her as "flat-chested Tsunade" during their childhood.

One of Tsunade's noteworthy possessions was the crystal necklace that belonged to her grandfather, which is said to be valuable enough to "buy three gold mines and the mountains on top of them" as stated by Jiraiya. On the twelfth birthday of her younger brother, Nawaki, Tsunade gave the necklace to him in the hopes that it would help him achieve his dream of becoming Hokage. The next day, Nawaki died as one of the many casualties of the war going on at the time, and the necklace was returned to Tsunade's possession. Sometime afterwards, Tsunade fell in love with a man named Dan, who also wanted to become Hokage. As a sign of her affection and in the hopes that it would help him achieve his goal, Tsunade gave him the amulet as well. Dan too would go on to die a bloody death during the course of the war, once again returning the necklace to her possession. Then late in the series, she and Naruto make a bet with the necklace as the ante. She loses the bet and hands it over to Naruto who remained owner of it until it was crushed by Naruto's six-tailed form. At some point in time she also made antidotes for Chiyo's poison which is very deadly but still cureable. This led Chiyo to be very uneasy towards her and calling her "that slug girl".

With the deaths of the two she loved the most, Tsunade came to lose faith in the title of Hokage, believing that only fools would want such a position. With these changes of ideals, Tsunade left Konoha with Dan's niece, Shizune, taking her in as her apprentice.

Personality
The deaths of Dan and Nawaki greatly changed Tsunade; Dan's death and her failed attempt to save him gave her hemophobia (a fear of blood), causing her to freeze upon seeing it (which very likely also impaired her summoning ability). The repeated returns of the necklace to her also led her and many others to believe that it was cursed, and whoever Tsunade might give it to would die soon after.

Tsunade is also a compulsive gambler who has the unfortunate disadvantage of having terrible luck. As a result, she has been elevated to a comical status as for the gross profits others have made off her misfortune and gambling addiction. In the rare instances that Tsunade hits a winning streak, she believes it to be a bad omen, and bad things do tend to happen to her or her comrades afterwards. (in Part I above the three 7s, there is a picture in a row of a frog (Jiraiya), a slug (Tsunade), and a snake (Orochimaru). The symbol on the back of her coat,, means "gamble", or "wager", as gambling is one of her favorite pastimes.

Tsunade typically projects a tough demeanor, even when facing great personal difficulty, and rarely compliments or praises people. She readily criticizes others for their faults, such as Naruto for his immaturity or Jiraiya for his perversion (though her habits are rarely any better). On occasion though, Tsunade shows sympathy for others, consoling Shikamaru that while he failed his mission to return Sasuke to Konoha, all of his teammates survived. This is also shown when she works hard in order to help heal Rock Lee so that he may continue to be a ninja. And despite her often harsh and exasperated attitude towards her former teammate, Tsunade's hard exterior crumbles when she learns of Jiraiya's death at the hands of Pain, the loss of her closest and most precious friend hitting her extremely hard as she realizes that she is now the last of the Sannin.

Tsunade has a pet pig Tonton, that is usually kept in the care of Shizune and though she doesn't speak human language, she seems to understand everything and react quite actively.

Search for Tsunade arc
After his failed invasion of Konoha, Orochimaru sought out Tsunade. Upon finding her, he asked her for a favor, though before he could specify what this favor is she declines, having already noticed his wounded arms. Trying again, Orochimaru asked her to heal his arms, explaining that the injury was a result of his carelessness when killing the Third Hokage. Shocked by this revelation, Tsunade prepared to kill Orochimaru, though he once again intervened by offering to resurrect her dead loved ones: Dan and Nawaki. Interested in this offer, Tsunade considered it, and was left a week to decide.

Soon afterward, Tsunade was approached by Jiraiya and Naruto Uzumaki who wanted her to become the next Hokage. After turning down the offer and ridiculing it, Naruto challenged Tsunade to a fight, enraged that someone could disrespect the title of Hokage due to his undying desire to become Hokage himself. Tsunade accepted and easily wins, though not before witnessing Naruto's attempt at using the Rasengan. Intrigued, Tsunade makes a bet with Naruto to master the jutsu in a week, and if he won, he would get the First Hokage's necklace. Naruto accepts the bet, and resumed his training. As the week progressed, Tsunade keeps a careful eye on Naruto's progress and all the while contemplated Orochimaru's offer. When the week was up and Naruto appeared to have failed in mastering the jutsu, Tsunade went to meet Orochimaru, though not before drugging Jiraiya to make sure he didn't interfere.

Upon meeting with Orochimaru, Tsunade asked that he not destroy Konoha when his arms were healed. Orochimaru complied, and Tsunade prepared to heal him, though was interrupted by Orochimaru's assistant, Kabuto Yakushi. Kabuto, being a medical ninja himself, was able to notice the killing intent of Tsunade's healing jutsu and as such knew that she really intended to kill Orochimaru. Her motives known, Tsunade revealed that she knew Orochimaru lied when saying he'd leave Konoha alone, and that she couldn't bring herself to allow it due to Nawaki and Dan having loved Konoha until the end of their days. While she had tried to forget this fact over the years, Naruto's determination and desire to be Hokage reminded her of their dreams, and she had decided to do whatever was necessary to protect those dreams.

With that, Tsunade attacked Orochimaru, though Kabuto fought her in his place. As the two trade blows, Kabuto began to realize that he was completely outmatched and decided to use her fear of blood to his advantage by slitting his wrists and thus making her immovable. As Kabuto began to beat on Tsunade, Shizune and Naruto came to her rescue. While both were easily defeated, Naruto was able to overcome his injuries and continued to protect Tsunade. Although Tsunade told him to run, Naruto refused, and manages to hit Kabuto with a perfected Rasengan in his effort to protect her, defeating Kabuto. As Naruto collapsed and is left near-death due to Kabuto's last attack, Tsunade rushed to his aid and attempted to heal him, not willing to allow him to die. Her efforts were successful, and Naruto claims the amulet he had now won before losing consciousness. Putting the necklace around his neck, Tsunade asked once more for its wearer to become Hokage.

Orochimaru, worrying about what kind of threat Naruto may become when he gets older, tried to kill him, though Tsunade blocked that attack as a human shield. Orochimaru inquired as to why she was protecting Naruto, to which she replied that Naruto would someday be Hokage and that she will not allow him to die before that happens. With that, Tsunade accepted the title of that she had been offered and overcame her fear of blood, her first action being to attack Orochimaru. Joining forces with the still drugged Jiraiya, the two attacked Orochimaru, with Tsunade eventually being the one to deal the finishing blow. Defeated, Orochimaru escaped, vowing to destroy Konoha once he's healed himself. Once Naruto recovered, the group returned to Konoha, Tsunade ready to take the role Dan and Nawaki so dearly desired, and secretly believing that Naruto would someday become a great Hokage.

Sasuke Retrieval arc
Soon after arriving in Konoha, Tsunade healed the wounds of Rock Lee, Kakashi Hatake, and Sasuke Uchiha. Once healed, Sasuke defected from the village so that he could go to Orochimaru, and Tsunade was forced to send out a group of Genin to stop him. She also used Konoha's reacquired alliance with Sunagakure to call in a favor for reinforcements, hoping to give the retrieval team some backup. Despite her efforts, the group ultimately failed, and Tsunade helped in healing their fatal injuries, bringing them back to full health. In the aftermath of Sasuke's betrayal, Sakura Haruno asked to become Tsunade's apprentice, which Tsunade gladly accepted.

Pre-Shippūden filler arcs
Tsunade appeared in numerous filler arcs, though she typically did nothing more than sending others out on missions, occasionally trying new ways of deciding who would go on a specific mission. Her goal during the filler arcs was to keep Naruto busy until Jiraiya came back to prevent him from going after Sasuke himself. In one filler arc, saved Team 10 from the Legendary Stupid Brothers with a quick display of her strength. In another filler, she summoned Katsuyu to deal with some impersonators of Rock Lee and Might Guy who had entered the village.

Part II
During the timeskip, aside from her duties as Hokage, Tsunade watched over Sakura and taught her medical ninjutsu and her signature chakra based super strength. After Naruto's return to Konoha after the timeskip, the village's elders questioned Tsunade's decision to allow Naruto to go out on missions when Akatsuki sought to capture him. As such, the elders forced Tsunade to allow one of the men of Danzo, a fierce opponent of the Third Hokage, to be teamed with Naruto. Not trusting Danzo, Tsunade assigned Yamato to lead Naruto and keep an eye on Danzo's addition to the team.

Later, when two Akatsuki members entered the Land of Fire; namely Hidan and Kakuzu, Tsunade mobilized the Niju Shotai to look for and, if possible, capture the Akatsuki duo. While capture never came to be possible, the Akatsuki members were both defeated. Tsunade later performed an autopsy on Kakuzu, and found Naruto's newest jutsu, Wind Release: Rasenshuriken to be too dangerous for use based on the damage done to Kakuzu's body and Naruto's arm. She explained that the attack had struck at a cellular level, causing extensive damage to the both of them, and regretfully told Kakashi and Yamato not to allow Naruto to use the jutsu again, lest his access to chakra be destroyed.

The Three-Tails Arrival arc
After finishing her autopsy on Kakuzu, Tsunade receives a report from a deceased ANBU captain about Orochimaru and Sasuke's whereabouts. She calls for Kakashi and puts him in charge of Team 8 to investigate. Later, she receives new information from Pakkun about the enemy's unique crystal jutsu. When asked to analyze it, she appears to know what it is from rumors she heard about.

Later as Tsunade feared, Naruto discovered about the mission involving Orochimaru and wanted to join. Without a second thought, Tsunade gave Naruto permission. While part of the reason for her decision was from what Jiraiya told her about Naruto, she too believed the same of him.

Soon afterwards, she receives the report on Shino's crystallized insect. She realizes that it is rumored crystal element.

Later, Tsunade receives even worse news that Team Kakashi has encountered the dreaded Three-Tailed Demon Turtle. Deciding that they needed to capture the beast quickly as to not let it fall into enemy hands, Tsunade orders Tenten, Rock Lee, and Ino Yamanaka to aid Team Kakashi in sealing the beast. Before sending them out, Tsunade made a large and special scroll to aid the team in sealing the beast.

Later, she also decides to summon and send out Katsuyu for even further assistance.

Hunt for Uchiha arc
When Jiraiya stated that he was going to do battle with the enigmatic Pain, Tsunade betted that Jiraiya would die, but said this jokingly, due to her horrible luck in gambling. Unfortunately, Jiraiya was defeated and killed during the battle, possibly making this one of the few bets Tsunade ever won. Before his death, Jiraiya sent a toad to Tsunade with a code which would reveal Pain's true identity. When Pa returned to Konoha with the results of the battle, he told her of Jiraiya's death. With both Jiraiya and Orochimaru dead, she is the sole surviving Sannin. After telling Naruto about Jiraiya's death Naruto quickly blamed Tsunade for his death, then stormed off afterwards. Tsunade is then shown telling Shikamaru to have Jiraiya's message decoded and was subsequently seen crying by herself, knowing she lost her closest and most precious friend.

Invasion of Pain
Tsunade requested the return for Naruto after finding out that Konoha was under attack. However, the village elders interfered who requested that Naruto was not to be alerted out of fear for him to be captured by the Akatsuki. Tsunade angrily grabbed them both by the collar, and responded by telling them that they couldn't treat him like a child forever and that Naruto has the will of fire that enables him to protect Konoha as well as being able to surpass Jiraiya. After mentioning that others had faith in Naruto's abilities which is something they never had, just as people before them had faith in them, they must entrust this faith to the future generation, and so Koharu Utatane reluctantly gave into her demands.

Tsunade was then informed by Shizune about a Chakra receiver found in Pain's body that is used to control the other Pains through a chakra transmission and Tsunade ordered ANBU to guard Shizune and the interrogation squad to complete the investigation into Pain's identity. Tsunade summoned Katsuyu and asked her to disperse into smaller slugs and take Tsunade's chakra to heal the injured. She then vowed to live up to her title of Hokage to protect the village with her life. As Tsunade was healing nearly all of the injured, one of the Katsuyu's slugs found Kakashi and Tsunade punches a wall in frustration knowing at how grim the situation looked for the village. Choji arrived to tell her the abilities of Deva Path. She then told Choji that Choza and Kakashi needed to be sent to the hospital immediately. When asked if Kakashi was alright, she gave no answer. Deva Pain arrived and stared at Tsunade coldly telling her that she's the last of legendary three. Tsunade looked at him in shock, and immediately recognized him from Amegakure.

Deva Path immediately demands Tsunade tell him where Naruto is, but Tsunade instead states that Akatsuki is nothing but a bunch of terrorists out to pursue their own goals. As she and Pain begin to voice their own views about how the Five Great Shinobi Nations turned out, Human path contacts Deva Path--revealing the location of Naruto--as Human path had managed to retrieve that information forcibly from Shizune. As Deva path decides to leave, he warns Tsunade that the wars started by the Five Great Nations will only continue to create more wars. He also says he will make Tsunade know pain and jumps up preparing a powerful technique.

Tsunade and the ANBU chase after Deva path, unaware that he was about to use his special jutsu at its ultimate level. As Deva path demolishes nearly all of Konoha, Tsunade has Katsuyu use its clones to protect as many people as possible from the blast. To do this she uses the excess chakra stored in the mark on her forehead. With the arrival of Naruto at the site of devastation, Deva Pain summons all other path bodies, including a newly revived Asura path to his side. Enraged by the destruction of the village, Tsunade confronts them and prepares to engage them in battle to fulfill her title as Hokage. Deva Pain ignores her challenge, and sends Asura Pain to impale her with its bladed arm. She is saved by Naruto, who crushes the Asura Pain body into pieces instantly with a Rasengan. Surprised by Naruto's new found strength, she sees the ghostly figures of Jiraiya and Minato Namikaze standing with Naruto. Naruto tells her as the Hokage, she doesn't need to dirty her hands with scum like Pain, and that he will defeat him.

Then when the battle begin, Naruto asks Gamakichi to take Tsunade to a safe place. Naruto also wants Tsunade to tell the villagers to not interfere the battle. Tsunade gives one of Katsuyu's clones to Naruto (Katsuyu knows the abilities of Pain's bodies, along with having some of Tsunade's chakra to heal Naruto if necessary), which Fukasaku quickly told to hide in Naruto's pocket. As Animal path summons the giant yak, Gamakichi takes Tsunade to Sakura, who called to her. But having used all her chakra, Tsunade reverts to her old, weak state, greatly worrying Sakura.

Transformation Technique
Even though she is in her fifties, Tsunade's Transformation Technique makes it appear as if she were still twenty (which Naruto calls "living a lie"). Tsunade's transformation is somewhat different from a normal transformation as it seems to be permanent, not getting dispelled when she is slashed or injured, and she apparently does not need to exert any effort to stay transformed, albeit it seems to temporarily shut down when her chakra runs low, as seen when she and Jiraiya were fighting Orochimaru.

Taijutsu and Chakra Control
Tsunade's trademark ability is her great raw strength, which is amplified even further with chakra control to inhuman levels. By storing chakra and releasing it at the point of contact, she can enhance her strength to the point where she can effortlessly break through boulders with her bare hands, make a huge crater by using her painful sky leg move and able to pick up Gamabunta's giant weapon. She is also renowned for her tremendous skill in taijutsu and has very good agility as shown when instantly bounced off a rock in her fight with Kabuto while just punching a hole in it a second earlier and was able to catch Orochimaru (who is not slow) when he was running from her and seemly because of her strength is able to leap pretty far distances as she can quickly close the gap between her and her opponent. She also seems to be quite fast because seconds after Kabuto hit her in her intercostals (which is used for breathing) she was able to appear behind him and hit him with a nerve attack without him noticing. She has also shown tremendous durability as she was still able to move regardless of her muscles being cut and take multiple stabbings from Orochimaru without being rendered unconscious. This combined with her strength makes her a truly dangerous kunoichi for anyone to face directly.

Medical Techniques
In addition to her unrivaled strength, she is equally impressive and renowned as the best in the world for her expertise as a Medical-nin, and can heal wounds that most others would consider impossible with relative ease. Her knowledge of the medical arts are so great that she can immediately determine what kind of injuries or illness a person has from a single glance as she did with Orochimaru when he came searching for her. Also she seems to know the human body very well as she develop a technique that can even attack the nerves itself. The most extreme example of her medical prowess is Creation Rebirth, a technique that makes use of the massive amounts of chakra available after using Yin Seal: Release to continuously regenerate the cells in her body, healing any wound and even growing back missing organs. It gives her a form of "immortality" in battle that even Orochimaru expressed envy for. It is because of these skills that she is regarded as Konoha's strongest kunoichi. However, because of the rapid cell regeneration, the technique shortens her life much like the Four-Tailed transformation and Deva Pain's technique, Shinra Tensei, at it's ultimate level as it was stated by Konan. Although she has more control over the process than Naruto's transformation. Because of the risk associated with the technique, Tsunade has made the choice to only use Creation Rebirth in extremely desperate situations.

Summoning Technique
Additionally, Tsunade can summon Katsuyu, a giant slug that is intelligent and very loyal to her. Katsuyu is able to perform a number of jutsu, such as spitting acid and splitting into smaller slugs, which can recombine to form the main body once again. Tsunade can use the slugs as a medium for her medical jutsu, allowing her to heal far more people than she can individually reach; the slugs can also be used to spread information. During the Invasion of Pain, she uses that to protect the villagers of Konoha. Tsunade was able to have Katsuyu surround herself around the villagers protecting them from Shinra Tensei.

Creation and conception
Tsunade's name is taken from the character of the same name from. The Tsunade in that story excelled in slug magic and was married to Jiraiya. The name means "mooring rope."

Trivia

 * Her young appearance is not because of a transformation but rather her powers of bodily manipulation by frequently changing her physical appearance to look like previous ages sometimes a teenager, a mature lady, or somewhere in between those ages.
 * Tsunade is the only Hokage whose last name is not yet known. Coincidentally, she used to be the only Hokage whose first name was known.
 * Despite her age, her stamina, vitality, and physical prowess still seems to be quite high. It is likely that her immense knowledge as a medical expert has allowed her to maintain youthful-like health.
 * Interestingly, when Tsunade reverts to her actual, elderly form, she becomes extremely weak and frail, while Jiraiya, who is always physically in his 50's, is not nearly as weak as Tsunade is while she is in this form. Though, this may be because Tsunade is only in her aged state when she is completely void of chakra, undoubtably contributing to her frailness.
 * Her surname apparently isn't Senju because even after her grandfather's name was revealed, she was still listed as Tsunade, not Tsunade Senju, in the databooks.
 * While Tsunade's english anime Voice Actor is Debi Mae West, in most games, she is voiced by Mary Elizabeth McGlynn, who is Kurenai Yuhi's Voice actor. The few games where she is voiced by her anime Voice actor are Naruto: Uzumaki Chronicles 2 and Naruto: Clash of Ninja Revolution.
 * As an add-on note to the above statement, in Naruto: Clash of Ninja Revolution 2, while being voiced by Mary Elizabeth McGlynn through out the story-line, during game-play, most of Debi Mae West's voice-overs from the first game are still used.
 * On the back of Tsunade's coat, there is a symbol depicting "kake", the kanji for gambling, within a red circle. This is quite appropriate for "The Legendary Sucker" seeing as she does indeed love to gamble.
 * Tsunade is the first female Hokage, and the first female Kage seen in the series.
 * Comically, whenever Tsunade wins the lottery or wins some money, it usually means something bad is going to happen. She herself even notices this and begins getting worried when she wins, such as when hitting the jackpot prior to seeing Orochimaru or winning the lottery during the first Shippuden arc when Gaara was kidnapped.
 * Tsunade is the granddaughter of the First Hokage, the grandniece of the Second Hokage and was trained by the Third Hokage.
 * According to the latest databook, Tsunade wishes to fight Naruto.
 * Because of Naruto's resemblance to Nawaki, Tsunade looks upon him as a typical mischievous little brother.

Quotes

 * "One of the Legendary Sannin taking on a snotty nosed Genin...I oughta be ashamed of myself."
 * "This is the Big One...where I bet it all...where I put my life on the line."
 * "One finger's all I need!"
 * "Jiraiya! Are you trying to teach this kid the Rasengan?! What's the point of teaching him this technique when he can't even master it? Filling his head with stupid dreams! To actually think that he'll become Hokage someday!"