Fū Yamanaka

was a shinobi from Konohagakure's Yamanaka clan as well as a high-ranking ninja of the disbanded ANBU faction: Root.

Personality
Like all other members of the ANBU faction, Root, Fū lacks a personality due to the gruesome training regime Danzō had them undergo at a young age. As such, he acts merely as a tool that carries out Danzō's orders. The only discernible trait that he and the other members have shown is fierce loyalty towards Danzō. As such, he was willing to face Tobi with Torune and Danzō without fear or losing his temper, or even take his own eye out, while possessing Ao's body, calling it a "small price to pay" in order to fulfil Danzō's orders.

Appearance
When first introduced, Fū's appearance was that of a regular Konoha ANBU, with a white cloak and mask. When he removed the mask it was revealed that he was a young man with auburn coloured hair and amber eyes. He wore a short black jacket with red straps on the shoulders, like all members of Root. This most likely shows allegiance to the organisation. He also wore a red short kimono under the jacket with a black sash, a pair of black gloves, dark-coloured pants, and regular shinobi sandals. 

Abilities
Danzō stated that he and Torune are two of the most-skilled ninja in Root. Fū also appears to be a skilled sensor, enough to detect Sasuke and Karin approaching the party gathered at the Kage Summit. His reflexes are fast enough that when Tobi reappeared he instantly sensed him and counter-attacked.

Fū is also an expert in trap making. He regularly uses this skill with a cursed seal variant of his clan's Mind Body Switch Technique, which he transferred his consciousness into a strange scarecrow-like puppet with kama and kuwa for limbs. He proceeded to use the scarecrow to attack Ao. Although seemingly easily defeated, Ao then found that a secondary ability similar to a Cursed Seal had triggered a switch of his consciousness with the scarecrow. All the while, Fū was unconscious and being carried around by his partner, Torune.

Five Kage Summit Arc
Danzō selects Fū and Torune to escort him to the Kage Summit in the Land of Iron. Once they arrive and the meeting begins, Fū comes to Danzō's defence during the Fourth Raikage's outburst and Zetsu's appearance. Zetsu informs them of Sasuke Uchiha's presence, and Fū and Torune try to go and eliminate them. The Raikage goes instead, so they stay with Danzō. Fū alerts Danzō when Sasuke's sensor locates them and subsequently flees with Danzō when Sasuke arrives at their location. They are pursued by Ao.

Danzō instructs Fū to stop Ao and safely retrieve his Byakugan. Fū lays several traps, including the Mind Puppet Switch Cursed Seal Technique, and once it activates he gains control of Ao's body. Ao's Byakugan, however, is protected with a seal that he cannot remove. Fū decides to just decapitate Ao instead so that he can take his head, but the Fifth Mizukage arrives before he can do so. Acting as Ao, Fū tries to convince her to remove the seal. The Mizukage, perfectly aware that Ao would never ask her to do this (because she is not able to), beats up Ao to release him from Fū's control, unaware that Fū has already left.

Nearing Konoha, Fū, Torune, and Danzō are ambushed by Tobi. While Danzō prepares for battle he has Fū and Torune distract Tobi. Fū tries to use the Mind Body Switch Technique, but Tobi teleports away before it can connect. Tobi stages a counter-attack and Fū slashes at him with his sword, but Tobi catches the blade. Torune throws a kunai at Tobi, forcing him to release Fū. Fū and Torune try attacking from different angles, hoping that one of them will be able to attack Tobi while Tobi is attacking the other. Tobi sees through their plan but plays along, causing Torune to accidentally infect Fū with his nano-sized, venomous insects. Torune cures him, but Tobi quickly sends them both away with his space–time technique.

Shinobi World War Arc
Fū was released by Tobi, who was held captive with Torune under a genjutsu, but during Kabuto Yakushi's explanation of the Summoning: Impure World Resurrection, he was used as a sacrifice to revive Torune's soul, at the cost of his own life.