That's the opening song, eX-Dream. Performed by Myuji, it's on the both X TV soundtracks (Japanese catalog numbers VICL-60822 and VICL-60823, also available in the US from Geneon records), the CLAMPAZAR CD collection (Japanese catalog number VIZL-131, not available in the US), and the single (Japanese catalog number VICL-35313, not available in the US).