>>58895258he was the head writer for the first three Pokémon movies and the first season of the anime. He absolutely hated the idea that Ash would never evolve or that the series was meant to go on forever, and he wanted to write a more “adult” story.
iirc thanks to the chaos caused by the Porygon episode he got the chance to push more mature themes in the first Mewtwo movie, where in the Japanese version Mewtwo isn’t really a villain but a clone questioning the meaning of his own existence, and Mew is kind of an asshole who argues for the superiority of the originals.
The third movie was supposed to have a completely different script. I won’t deny that some of his ideas were a bit edgy, like Pokémon rebelling against humans, but he genuinely wanted to write something with depth instead of just a kids’ cartoon. Also, I think he wrote Team Rocket’s intro monologue.