I will not have you refer to mother that way!
- —Yazoo to Reno
Yazoo is one of the three Remnants of Sephiroth, along with Loz and Kadaj, who are the antagonists of Final Fantasy VII: Advent Children. He embodies Sephiroth's allure, and has a cool demeanor. Yazoo often battles alongside his brothers in numerous battle scenes, and is the quietest remnant.
Yazoo wears a long black coat zipped up over his chest with black boots, shoulder guards and straps crossing over his torso. His silver hair is long and extends partway down his back, although not as far as Sephiroth's hair, and he has green eyes with cat-like pupils, the same as Sephiroth. He fights using a Velvet Nightmare handgun, and is the tallest of his brothers and is very lean. Because of his height, hair, and outfit, Yazoo resembles Sephiroth the most of the three remnants.
Just as soon as you give back Mother, that'll be the end of everything.
- —Yazoo to Reno.
Yazoo embodies Sephiroth's allure and cool personality, and pains were taken during writing to differentiate his personality from Kadaj's while not making him like Loz, who was characterized as child-like. Yazoo has few facial expressions, limited to moments such as when Reno insults Jenova, or when Cloud Strife slices apart his Velvet Nightmare gun.
Yazoo first appears looking over the wasteland around Midgar with his brothers, and attacks Cloud with Shadow Creepers and Loz. Although they appear to gain the advantage, Kadaj calls off the attack after speaking to one of the Turks on the phone, but not before Yazoo shoots Cloud point-blank in the face, his shot deflected by Cloud's goggles, However Cloud still sustained a minor injury, which is shown as blood is seen trickling down his face.
While Kadaj and Loz go elsewhere to search for Jenova, Yazoo goes to Edge and rounds up dozens of children infected with Geostigma, promising to help cure them. In actuality, the children are needed for a Jenova reunion. Yazoo takes the children to the Forgotten Capital, where Kadaj takes control of them.
When Cloud arrives to save the children, Yazoo and Loz battle and easily overwhelm him, he is saved by Vincent Valentine who takes him to safety. The remnants and the children return to Edge, where Yazoo and Loz attempt to destroy a monument to Meteor, where they believe Rufus has hidden Jenova's remains. Reno and Rude attack them, and Yazoo easily defeats Reno. Kadaj summons Bahamut SIN to terrorize the city, and once defeated by Cloud, Rufus reveals Jenova's remains to Kadaj.
Kadaj and his brothers drive onto the highways into Midgar to flee Cloud, and Yazoo and Loz attack him to stall him. After steering Cloud onto a second highway from the one Kadaj takes, a high-speed battle takes place, both on their motorcycles and in the air above them. Reno and Rude arrive via helicopter to assist Cloud and destroy the section of highway the Remnants are driving on. This creates a ramp for Yazoo to launch his motorcycle off, passing through the helicopter's opened section, shooting off the control stick from under Reno's hand and knocking Rude to its outer edge, giving a high-pitched insane laugh all the while.
Cloud takes on both Yazoo and Loz with his sword later, forcing them to share a motorcycle and to lose their primary weapons. The Turks shortly after catch up in a second helicopter and use bombs to seemingly kill Yazoo and Loz. They, however, somehow survive, reappearing after Cloud defeats Sephiroth and shoot him. Yazoo and Loz then use many Materia to create an explosion before vanishing, killing themselves in the process.
Yazoo is quick and agile, swift enough to both evade Cloud's attacks with the Fusion Swords and to momentarily step on the blades to leap away. Yazoo usually fights from a distance while shooting opponents up with the Velvet nightmare, relying on his agility to dodge blows in close-range. Yazoo is an extremely skilled marksman, able to shoot Cloud's goggles off his face at point-blank range while only scratching Cloud's face. His long-ranged and agile preferences compliment Loz's hand-to-hand power tactics when they fight together.
Yazoo's long hair was a significant difficulty to animate due to its layers and length, and along with Sephiroth his hair was animated by hand during fight scenes because a simulator would not be accurate enough. The staff wanted to make Yazoo stand out on his own without being too much like Kadaj or Loz, and gave him his unique appearance from either of them as part of this. Despite having a cool personality, Yazoo was made to banter with Loz to provide comic relief from the film's generally dark tone.
Yazoo's Japanese voice actor is Yuuji Kishi, while Dave Wittenberg voices him in the English release. Tetsuya Nomura wanted a shady, dangerous quality to Yazoo's voice, rather than a cool or charismatic voice. Kishi notes that Yazoo's fight scenes were difficult for him, as he had to get the timing of the breathing just right, and the film would be played for him with his mouth superimposed over Yazoo's as an aid. Dave Wittenberg later voiced Kefka Palazzo in the Dissidia series, as well as Amodar in Final Fantasy XIII.
Yazoo appears in Final Fantasy Trading Card Game.
Yazoo's name comes from the geological term, "yazoo stream", referring to a small river that runs alongside, and eventually joins, a much larger river. This likely refers to Yazoo's existence as a part of Sephiroth, although it may also refer to his eventual dissolution into the Lifestream.
Yazoo is also a popular British synthpop band fronted by Vince Clarke and Alison Moyet (known as Yaz in the United States) from the early 1980s. This may be relevant since there already are My Bloody Valentine and Velvet Underground references within Final Fantasy VII.