Mr. Yamamoto is Julie's father.
Mr. Yamamoto looks Chinese and wears a blue shirt with a white undergarment underneath the shirt. He has a black mustache and eyebrows. He has wrinkles all over his face and a mixture of black and white hair. He looks strict.
Mr. Yamamoto doesn't seem very fond of Ben, but he still seems to approve of his relationship with Julie. This reflects on how Gwen's parents aren't fond of Kevin, but they still approve of Gwen and Kevin going out.
Mr. Yamamoto appears in The Perfect Girlfriend to inform Ben that Julie isn't home and that Ben should know where she was, when Ben asked him where Julie was.
Ben 10: Ultimate Alien
- The Perfect Girlfriend (first appearance)