The Cursed Warrior was a ghostly samurai who supposedly came from the Land of Birds.
It was believed to be the ghost of the country's former daimyō, Ōwashi. Ever since Ōwashi was discreetly poisoned by the Watari ninja Hoki, taking the disguise of Mōsō, the Cursed Warrior had been haunting the Land of Birds and attacking Mōsō and several other of its inhabitants. Mōsō sent Chishima to Konohagakure to gain help from its ninja to stop the cursed warrior. Tsunade sent Naruto Uzumaki, Neji Hyūga, and Tenten to the Land of Birds to help out. Overtime, the people and Team Neji began to suspect Kōmei, the Land of Birds' tactician, was behind the Cursed Warrior. During the first battle with Team Neji, after being attacked for a short while, vanished completely, leaving the empty armour behind. Also, Neji said that there was no human presence inside.
By the second encounter, Team Neji discovers Kōmei near the Cursed Warrior and fled when the Cursed Warrior attacks. Neji uses his Byakugan to discover an unidentified person in it (later revealed to be one of Hōki's unnamed henchmen). Using the Naruto Barrage, Naruto defeats the Cursed Warrior. However, slime pours out of the armour showing that the unknown wearer had bailed out at the last minute. The next morning, Kōmei is taken into custody.
When Naruto had been imprisoned by Sagi, Naruto had a brief encounter with the Cursed Warrior and ended up discovering that it's Sagi in disguise. Before Sagi could finish off Naruto, a wounded Chishima arrived and told Sagi about Mōsō's plot. When Kōmei was about to be executed, a fog came in and the Cursed Warrior arrived and abducted him. Neji and Tenten followed the Cursed Warrior to Sagi's palace and discovered that Naruto was in the Cursed Warrior armour. When Sagi plans his final move on Mōsō, it is revealed at this point that he was actually his twin sister Toki in disguise and that the real Sagi had died. When Sagi in the Cursed Warrior armour appeared at Mōsō's house to attack him, he was no match for Mōsō who managed to use his fake jutsus to trap him and a fireball jutsu that knocked off the Cursed Warrior mask. When Naruto, Tenten, Neji and Kakashi Hatake arrived and fought the Watari ninja, the Cursed Warrior helmet is knocked off by another attack revealing to Mōsō and Naruto that Sagi was actually Toki.