Shinji is a trainer from Sinnoh who travels around challenging other trainers. He first showed up in the Diamond & Pearl series during "Two Degrees of Separation," though viewers got the full picture of who he was in the next episode, "When Pokémon Worlds Collide."
Right from the start, Shinji comes across as the kind of trainer who's all about winning and making his Pokémon as strong as possible—basically the opposite of how Ash approaches things. He doesn't really care about bonding with his team or what they want; he just wants power. This attitude is exactly what sets Ash off. Their rivalry becomes a major storyline as Ash keeps challenging him, determined to show him that his way of training is wrong.
The two of them finally settle things with a six-on-six battle, and Ash pulls off the win. After that, their rivalry basically ends—at least as far as the show portrays it.
Content compiled by AnimeList.moe from publicly available sources.
