Yashamaru (夜叉丸) was a medic-nin from Sunagakure, and as the younger brother of Karura, he is also the maternal uncle of Temari, Kankurō, and Gaara.
Background After his sister was sacrificed to seal the One-Tailed Shukaku, Yashamaru was assigned by the Fourth Kazekage to be Gaara'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. In reality, however, Yashamaru hated Gaara, never having been able to get over the loss of his sister. When the Fourth Kazekage asked him to assassinate Gaara, due to the boy's uncontrollable powers being a threat to the village, Yashamaru willingly accepted the command in order to avenge Karura. The assassination attempt, however, ended in a desperate suicide mission with Exploding Tags on his body, which ultimately failed. After being injured by Gaara's Sand Binding Coffin, and before detonating the tags, 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 will 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.
Yashamaru loved his sister, Karura, above all. He tried to love Gaara, but could never let go of the fact Karura died giving birth to him.
Yashamaru, like Itachi, was able to hide his emotions well. He may have seemed kind, and 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. In truth, Yashamaru was unforgiving and murderous towards his nephew, and always hated him. He was willing to sacrifice his life to avenge his dead sister.