Hattori Kinzō is a character appearing in the second episode of the OVA Mutant Turtles: Chōjin Densetsu Hen.
Hattori is the leader of a clan of Ninja and an old friend of Splinter's who lives in Shinobi Village in Japan. When Hattori sends a message to Splinter for help, Splinter, April O'Neil and the Turtles all fly to Japan. Once they've arrived at Shinobi Village, Hattori tells them he needs help with a set of Magatama he has that are embedded into a magic mirror called the Mi-Yuu-Tai-Shi, which sounds like Myuta-Ishi, or Muta-Stones.
Shredder shows up with Bebop and Rocksteady to steal the mirror. To protect it, Hattori causes the castle to grow taller, with the mirror on top of the roof. Everyone realizes that they have to climb the castle and lay claim to the Magatama before the other side does, and despite a valiant effort by Kinzo's ninja crew, Shredder's group gets to it first and use three of the stones to transform. The Turtles use the four remaining stones to transform and fight back. The sides are pretty evenly matched, but as Kinzo reveals, they can only stay in their Metal Form for six minutes, and since Shredder and his men transformed well before the Turtles made it up to the roof, this puts them at a significant disadvantage.