Nawaki

was the younger brother of Tsunade and the grandson of the First Hokage.

Background
He was very much like Naruto Uzumaki in both appearance and personality, and, like Naruto, Nawaki also had the dream of becoming Hokage one day. He shared this dream with his sister on his twelfth birthday, who gave him their grandfather's necklace in the hopes that it would help him achieve his dream. The day after his birthday, Nawaki died in battle after running into an explosive trap. Orochimaru was with him, along with two other genin, implying that Orochimaru had a genin team, with him as a member. His body was so heavily mutilated that it was beyond recognition. The necklace was retrieved by Orochimaru and returned to a devastated Tsunade.

Search for Tsunade arc
Orochimaru would later offer to Tsunade to bring Nawaki back to life, together with Tsunade's lover, Dan, in exchange for healing his arms. The resurrection would require a human sacrifice, though. She ultimately refused, realizing that Nawaki and Dan would not want her to sacrifice the lives of others in exchange for theirs.

Trivia

 * Nawaki made a cameo appearance in the ending omake of Shippūden Episode 129, holding a balloon portraying Tsunade's face.
 * His hair was made shorter and darker in the anime to make him less resemble Naruto.