Fū Yamanaka

(Foo in the English manga) is a ninja of Konohagakure, and a seemingly high-ranking member of the Foundation.

The Summit of the Five Kage arc
Fū is hand-picked by Danzō, along with Torune, as one of his unmasked escorts, to protect him during his journey to the Kage Summit in the Land of Iron.

Before departing, Fū asked Danzō about how they should prepare for the trip; Danzō told him to not worry about it and prepare in any way he sees fit.

Later, he is seen walking with Danzō and Torune, and the group is attacked by the Hanya Assassins from the Land of Wood. Danzō tells them not to do anything and brutally defeats all the assailants. When the Raikage became too violent, he and Torune, along with the other kage escorts, jumped into a defensive stance. He was told by Danzō to stand down. When White Zetsu appears during the summit, Fu and Torune guard Danzō. When him and Torune try to go and battle Sasuke they are stopped by Ao who was told to watch them  by Raikage  him and Torune try to attack but are stopped by Danzō. He later reveals to Danzō that their location has been found out by a member of Sasuke's squad, and he asks what they should do, to which Danzō replies that they stay where they are, and if attacked, they could use the confusion to escape. When Sasuke and Karin get to where the summit is taking place, Fū, along with Torune and Danzō, escape but they are chased after by Ao.

Realizing this, Fū sets several traps in preparation for his special jutsu. Before activating it, Danzō orders Fū to make sure to not damage Ao's Byakugan. Fū then proceeds to transfer his mind to his puppets and begin his assault on Ao. After luring Ao close enough, Fū takes control of Ao himself. Unfortunately, he is unable to remove the Byakugan eye because of a special seal protecting it. Fū improvises by instead deciding to decapitate Ao.

Fortunately, the Mizukage arrives in time to save Ao. Hoping to trick the Mizukage to remove the seal, Fū pretends to be Ao. The Mizukage is able to see through the lie and beats up Ao's body to free him, unaware that Fū already ended the jutsu.

Abilities
Fū appears to be a sensor. He is skilled enough to detect Sasuke and Karin planned to approach them, and that Karin is a sensor type.

Fū is also an expert in trap making. He regularly uses this skill with a jutsu similar to the Yamanaka clan's Mind Body Switch Technique, the Mind Puppet Switch Cursed Seal Technique, in which he transferred his consciousness into a strange scarecrow like body with kama for limbs and proceeded to attack Ao. Although seemingly easily defeated, Ao then found that a secondary skill similar to the Cursed Mark switched his perception with the scarecrow. All the while, Fū was unconscious and being carried around by Torune, much like the Yamanaka technique.

Although Fū has not been shown using any other jutsu yet, Danzō stated that he and Torune are two of the most-skilled ninja in Root.