Shizune

is the assistant of Tsunade and a talented Medic-nin. Shizune is quite close to Tsunade, one of the few people Tsunade will trust with absolute certainty and a fairly talented and capable ninja in her own right, often using jutsu involving poison (such a Poison Mist and Prepared Needle Shot).

Background
Shizune is the niece of Dan, the lover of Tsunade. Sometime after Dan died, Tsunade left Konoha and Shizune went with her as her attendant. The bond between Tsunade and Shizune is so strong that above all, Shizune sees her purpose in life is to take care of Tsunade. Besides being Tsunade's attendant, she is also a highly talented medical-nin and jōnin. Her talent in the medical field is rivalled and less than the abilities of Sakura Haruno and Tsunade herself.

Personality
Unlike Tsunade, she is level-headed, practical, and a rational thinker. As a result, she is the one who tends to stress over details like Tsunade's tendency to gamble and think with her heart. She often gets comically worked up over any irrational decision Tsunade makes. Shizune also looks after Tonton, Tsunade's pet pig.

Search For Tsunade arc
When Orochimaru comes to Tsunade years later in an attempt to get her to heal his arms, Shizune attempts to persuade Tsunade against it, even trying to convince Tsunade to help her kill Orochimaru. When all attempts to persuade Tsunade fail, Shizune tries to use force to stop Tsunade from helping Orochimaru, though Tsunade easily defeats her. She later fights with Kabuto Yakushi in an effort to protect an incapacitated Tsunade and Naruto Uzumaki, but Kabuto proves too much for her as he easily dodges her attacks and incapacitates her as well.

Sasuke Retrieval arc
When Tsunade takes on the title of Hokage, Shizune leads a team consisting of Genma Shiranui, Raido Namiashi, and Iwashi Tatami to compensate for the lack of manpower caused by the invasion of Konoha. When Genma and Raido are defeated by the Sound Four, Shizune heals their wounds. Later, she is seen leading a medical team charged with regenerating the wounds of Neji Hyuga.

Anime Filler arcs
She appears in almost every filler arc as an attendant and secretary of the Fifth Hokage,Tsunade. She is seen to be part of a reinforcement team for Naruto, Choji and Hinata during the Vegtable Country arc.

Sai and Sasuke arc
Shizune expresses concern in Tsunade's decision to allow Naruto to go out on missions, and reports this to the village elders. Although Tsunade is able to reach a compromise with the elders, Shizune doubts Tsunade's wisdom, though she does seem to regain faith later on.

Pain's Assualt on Konoha arc
Shizune is seen studying one of Pain's "bodies" and tries to determine what kind of science that has been used on this body. When Shizune discovers that the piercings on the body are chakra receivers she tells the news to Tsunade who concludes that the receivers are a key to Pain's strength. She then rushes with an Anbu to the Interrogation building to find more info on Pain. When she arrives, she along with the Anbu, Ino and others are attacked aby Animal Path and Human Path. When finding the situation critical, she feels that the information Inoichi has gained will help piece together the truth about Pain.

Other Appearances
She is seen in almost every Naruto video games so far. She is seen be able to create swords out of chakra call "Chakra Swords: Great Cross Slash" that causes both physical damage and internal damage to her opponent and creates a huge explosion. She also has a jutsu called "Hog Style: Tonton" which calls on Tonton to attack Shizune's opponent, hitting the opponent up to 30 times and causes major damage to her opponent.