The episodes use eight pieces of theme music: four opening themes and four ending themes. The first opening theme is "Ai wa Kurayami no Naka de" (愛は暗闇の中で?, lit. "Love is Within the Darkness") by Zard until episode 504. The second opening theme is "Ichibyō goto ni Love for you" (一秒ごとに Love for you?, lit. "Every Second I Love for You") by Mai Kuraki until episode 514. The third opening theme is "Mysterious" by Naifu until episode 520. The fourth opening theme is "Revive" by Mai Kuraki starting episode 521 and through episode 523. __TOC__