Sooner or later, Takato and his friends would have to face a force whose very existence threatens the world... our world, the digital world, or perhaps even both.
At a time like that, what would adults be doing?
The reason that Yamaki appears from the first episode was because I wanted to bring in the idea of adults doing their part to help Takato and the others face danger. At first, Yamaki appears as an "unpleasant adult" who is antagonistic towards the children.
In terms of models or inspirations for his appearance, I had in mind a trench coat-clad character played by Renji Ishibashi in a drama series I had once seen.
I wanted to show the story from the viewpoint of the children, so I decided not to show Yamaki's face. Only his voice and part of his body would be visible. As I needed a little something more, I gave him the habit of flicking the lid of his Zippo lighter. Later on, I realized that the metallic sound and the hidden face made him very similar to a character from the movie "E. T."... not that I'm a huge fan of that movie.
In the script, I decided that Yamaki would first remove his sunglasses in episode 24 ("The Journey Begins"). I found out that Mr. Nakatsuru, the character design artist, had drawn the subtle emotions expressed by Yamaki in this scene, and was very grateful to him.
Mr. Susumu Chiba, who played Yamaki in the Japanese, was spot-on as he portrayed the psychological strength and arrogance of a young, confident man still in his prime.