This episode is considered "filler" (anime-exclusive) and marks the start of the Cursed Warrior arc.
Tsunade assigns Naruto, Neji, and Tenten to the Land of Birds to investigate a ghost known as the "Cursed Warrior" that is terrorizing the population. Upon arrival, they discover the daimyō has recently died and his successor is neglecting his duties. Naruto (Dub) Episode 162
During a chase, Neji uses his Byakugan and realizes the armor the Cursed Warrior is wearing is completely empty. Naruto (Dub) Episode 162