A New Oath (Japanese: 新たなる誓いAratanaru Chikai) is the Japanese opening and ending theme for The Legend of Thunder!. The acoustic version of the song is used as the opening theme, while the full-length version is used as the ending theme.
The Pocket Monsters logo, "ポケットモンスター" (Pocket Monsters), appears together with "クリスタル" (Crystal), shines, then changes to the title "ライコウ 雷の伝説" (Raikou - Legend of Thunder). Jimmy is looking at a stadium, then he shows a Poké Ball. His Typhlosion is battling a Nidoking. Vincent, Marina and Jimmy are in a flashback, with their starters (Chikorita, Totodile and Cyndaquil). Jimmy is seen losing a battle against Silver. Jimmy and his Cyndaquil are running, Cyndaquil evolves to Quilava, then to Typhlosion. After becoming stronger, the duo wins a battle against Silver, and celebrates. A bolt of lightning is seen. Attila and Hun are seen. Jimmy's Typhlosion battles Hun's Steelix and Attila's Skarmory. Marina poses to the camera. Vincent appears. Professor Sebastian and Eugene are looking at the sky. Jimmy is holding a Poké Ball, and his Typhlosion appears. Attila's Skarmory, Hun's Steelix, Jimmy's Typhlosion, Marina's Misdreavus, Vincent's Meganium, and Raikou are seen. Marina, Jimmy, Vincent, their Pokémon and Raikou appear.