Zaku Abumi was a Genin-level ninja from Otogakure who participated in the Chunin exams with the intent to assassinate Sasuke Uchiha. Like many Sound ninjas, Zaku had undergone physical enhancements that amplified his abilities. Specifically, he had hollow air tubes installed in his arms that extended through his hands, allowing him to release a combination of air pressure and sound waves controlled by his chakra.
Unlike his teammates, Zaku's backstory was explored, making him a more dramatic character. He was an orphan living on the streets, surviving by stealing and often enduring beatings. Orochimaru recognized his potential and admired the strength in his eyes, which led to Zaku joining his ranks. Despite the hardships, Zaku never gave up, even at the cost of his own life.
After saving his teammate Dosu from Rock Lee's Lotus attack, Zaku fought Sakura when she tried to stop him from killing Sasuke. After defeating her, his team faced off against Team Asuma. When Sasuke regained consciousness and learned that Zaku had injured Sakura, he dislocated and severely damaged Zaku's shoulders. Zaku was the only Sound ninja to engage Sasuke directly, as the others retreated.
In the preliminary exams, Zaku battled Shino Aburame despite his shoulder injuries. His arrogance led him to attempt an attack on both Shino and his approaching swarm of Kekai insects. However, the bugs had already infiltrated the air tubes in his arms, preventing him from attacking and rendering his arms useless. In the manga, his right arm was blown off while his left was partially sliced. In the anime, both arms remained intact but riddled with holes, achieving a similar debilitating effect.
Dosu vowed to avenge Zaku's severed arms but failed to do so. Eventually, Zaku, along with Kin Tsuchi, was sacrificed by Orochimaru for the Impure World Resurrection, summoning the First and Second Hokages to fight against the Third Hokage.
