Yashamaru

was an ANBU and medical-nin from Sunagakure.

Background
After his elder sister Karura died shortly after giving birth to Gaara whom the One-Tailed Shukaku had been sealed into before his birth, Yashamaru was assigned by the Fourth Kazekage to be his youngest nephew's caretaker. At first, Gaara thought that Yashamaru was the only one that cared about him. Yashamaru taught Gaara about physical pain, emotional pain, and love - concepts Gaara was completely unaware of in his childhood.

As the Fourth Kazekage's right-hand-man he was tasked to assassinate Gaara, due to the boy's uncontrollable powers being a threat to the village. Yashamaru accepted the command but the test, ended in a desperate suicide mission, which ultimately failed. After being injured by Gaara's Sand Binding Coffin, and before detonating the series of exploding tags hidden under his flak jacket, Yashamaru explained how much he always hated his youngest nephew, and why his sister named him "Gaara": under the phrase of "A self-loving carnage", for her intense hatred against the village, and not love for her son. Yashamaru then stated that no one would ever love Gaara, and his last words, to Gaara, were, "This is it. Please die." Yashamaru's cruel words and his suicide bombing attempt on Gaara's life caused Gaara to become a sociopath and an even more of an emotional wreck than he already was.

Though Yashamaru's final words were hurtful, they were in truth lies as part of a plan formulated by the Fourth Kazekage, to corner Gaara psychologically, and lie about Karura's feelings in order to test if Gaara would lose control or not. Yashamaru who unwillingly but dutifully accepted the task himself felt that it was not a wise idea to do so. It is revealed that Yashamaru truly loved Gaara and believed that Karura's will lived on in the sand, protecting Gaara.

Personality
Yashamaru was a very warm and caring person and loved his sister Karura, above all. Under the test set by the Fourth Kazekage, Yashamaru claimed that he tried to love Gaara, but could never let go of the fact Karura died giving birth to him. He was seemingly the only person to understand Gaara for his accidental attacks on the villagers, and trying to persuade others to understand as well, while teaching him about love and pain. He was also willing to sacrifice his own life in order to test out Gaara's control over Shukaku, acting as though he was unforgiving and murderous towards his nephew, and always hated him, ending their relationship with bitter and aloof lies.

The person Yashamaru truly hated was his brother-in-law, the Fourth Kazekage, for implanting Shukaku within Gaara while still in his sister, and thus taking away Karura's life from Yashamaru. However, as an ANBU and the right-hand man of the Kazekage, Yashamaru still did as he was ordered, even acting as to betray his own nephew.

Abilities
As a medical-nin, Yashamaru is very adept at manipulating chakra, as seen with him controlling kunai in mid-air.

Trivia

 * In the Polish, Portuguese, Brazilian and Italian versions of the Naruto manga, Yashamaru is portrayed as female rather than male. Even in the English anime, there is no clear indication of his gender, despite the fact that he is voiced by a man.
 * Yashamaru's name, 夜叉丸, is composed of three Kanji. The first two, refer to creatures in Japanese mythology known as Yaksha. The Hindu version of the Yaksha usually portray them as having two sides: a darker, more sinister side, and a benevolent, lovable side. Yashamaru's betrayal could be a reference to this "dark side" of Yaksha.  is a common ending for male names.
 * Yashamaru, along with many other characters within the Naruto series, made a cameo in the ending omake of Shippūden Episode 129.
 * The databook initially listed Yashamaru as a chūnin but in chapter 548, he was stated to be an ANBU.

Quotes

 * (To Gaara) "A wound of a heart is different from a flesh wound. Unlike a flesh wound, there are no ointments to heal it, and there are times when they never heal."
 * (Last words to Gaara) "This is it. Please die."