Katazu is a swordsman who took his twin brother Kageki's identity after the accidental death of Shikazo. Kageki had loaned money to Shikazo but after the birth of his child, he asked to be repaid by him but Shikazo refused and a scuffle broke out which resulted him hitting his head on a rock hard enough to kill him. Kageki went to Katazu after that and he took his brother's identity while Kageki and his family went into hiding. Katazu purposely attracted Shikazo's pursuers while they went into hiding. Since then, Tsukado was tasked by his clan to carry out a vendetta against him but failed to defeat Katazu 34 times. The next day, Kanabun brought Katazu to Tsukado to profit off their fight. With Naruto's help, Tsukado was able to get the advantage but Naruto stopped their fight, noticing that Katazu couldn't have killed Shikazo. Katazu reveals the truth to Tsukado and he decides not to kill him. Kanabun and his gang try to force the two to fight again but the swordsmen and Team 7 chase them out of town.

(source: Narutopedia)