Yamato

is the temporary leader of Kakashi Hatake's Team 7, consisting of Naruto Uzumaki, Sakura Haruno, and Sai. "Yamato" is actually a codename given to him for the purposes of joining Team 7, his real name being. Yamato, however, seems to prefer going by his codename while near his teammates.

Background
Shortly after his birth, Yamato was one of 60 people kidnapped for the purposes of becoming a test subject of Orochimaru. In Yamato's case, Orochimaru injected him with the First Hokage's DNA in the hopes that he could replicate the First's ability to use Mokuton techniques, as well as an unquantified ability to control tailed beasts. Orochimaru was forced to flee Konoha before he could finish his experimentation, but believed that all of his test subjects had died. Yamato, however, was the lone survivor, and found himself endowed with the First's abilities. Yamato would go on to join the ANBU, and for a time he would serve under the guidance of Kakashi Hatake. Yamato would also come to have the best performance record of any ANBU serving under the Third Hokage, leading the Third's successor, Tsunade, to have the utmost confidence in Yamato.

Personality
Like other ANBU members, Yamato projects a calm, stoic demeanor in stressful situations. Despite this, he can also be quite laid back when not on duty, and is not above using his Mokuton techniques for creature comforts such as making a house to "camp out" in. While he has been good natured so far, Yamato claims to be a different sort of leader than Kakashi, one who is not above "ruling by the use of terror" when his team misbehaves. Aside from his obviously intimidating skills as a ninja, however, this "terror" has so far primarily consisted of casting a creepy "ghoul-eyes" expression directed at his charges, which seems more humorous than terrifying. Naruto, however, is easily creeped out by it. Yamato also seems to have an attachment to money, not wanting to spend on others unless he has something to gain.

Sasuke and Sai arc
Yamato is assigned to lead Team 7 in meeting with one of Sasori's spies within Orochimaru's ranks. Naruto and Sakura find it difficult to work with their newest team member Sai, and much of Yamato's time is spent trying to get them to cooperate. Upon arriving at the arranged meeting place, Yamato goes ahead dressed as Sasori to make meeting with the spy easier. After the spy arrives, who turns out to be Kabuto Yakushi, Yamato is able to learn a great deal of information until Orochimaru shows up. Just as Yamato starts to contemplate how he will fight Orochimaru and keep up his act as Sasori, Kabuto cuts off the head of the Sasori costume, having hoped to kill the real Sasori.

Faced with a combined attack from Kabuto and Orochimaru, Yamato creates a wood clone to escape, causing Orochimaru to realize that one of his test subjects had survived. A battle between Orochimaru and Naruto ensues, and Yamato spends much of his time protecting Sakura. When the battle is over, Sai is found to be missing, though a wood clone that Yamato has following Sai reveals that the latter has joined with Orochimaru. As the clone follows Sai to Orochimaru's hideout, the rest of Team 7 follows the clone. Once they arrive, Yamato uses his Mokuton abilities to infiltrate the base. When they eventually find Sai, they restrain him and are able to learn about Sai's real mission: to join forces with Orochimaru on behalf of his organization, Root, in an attempt to destroy Konoha.

Sai is eventually freed by Kabuto, who in turn is restrained by Sai. Sai, touched by Naruto's words about Sasuke Uchiha, rejoins Team 7 in their other mission of retrieving Sasuke. When the group splits up again, Yamato discovers a bingo book when going through some of Sai's belongings. In doing so, Yamato learns that Sai once again has an ulterior motive: to kill Sasuke Uchiha. In desperation, Team 7 goes looking for Sai, hoping to stop him from fulfilling his mission. Sai, however, really has had a change of heart, and attempts to bring Sasuke back to Konoha on Naruto's behalf. Due to Sasuke's exponential growth in fighting abilities, however, Sai is no match for him.

Due to an explosive attack from Sasuke, Team 7 is able to find Sai and learn that he really has allied with them. Upon failing to persuade Sasuke to return to Konoha, the team decides to use force instead. Sasuke's growth, however, is too much for the four's joint effort, and he is able to repel them all. After a brief confrontation between Naruto and Sasuke, Yamato attempts to capture Sasuke with his Wood Release: Wood Locking Wall, though Sasuke is able to escape. As an answer to this, Yamato declares that he had no intention of getting too rough on him in front of Naruto and Sakura, but has no choice. Despite this, Sasuke prepares what appears to be a finishing move, Orochimaru and a freed Kabuto arrive to stop him, and they disappear to leave Team 7 defeated.

Hidan and Kakuzu arc
After returning to Konoha, Yamato is recruited by Kakashi to help with Naruto's training in creating a new jutsu. In addition to being able to create training devices for Naruto with his Mokuton abilities, Yamato is also able to subdue Naruto if he loses control of the Nine-Tailed Demon Fox's chakra. Once Naruto completes the initial stages of his training, he moves on to perfecting his preexisting Rasengan. Kakashi, however, is not able to oversee Naruto in these final stages due to his volunteering to help Team 10 in the fight against Akatsuki. As such, he leaves Yamato in charge of the jutsu's perfection. Yamato is able to give advice in the jutsu's creation, and eventually bears witness to the fruits of Naruto's training.

Once Naruto has perfected his jutsu enough to be used in battle, Yamato, Naruto, and the rest of Team 7 join Kakashi and Team 10 in their battle. After teaming up with Naruto to stop an attack by Kakuzu, Yamato convinces Kakashi to allow Naruto to fight Kakuzu alone. Once Naruto is successful in defeating Kakuzu, Yamato joins everyone else in returning to Konoha.