
Quick answer — Nana Mizuki performed 6 anime themes, including "CRIMSON BULLET" from Magical Girl Lyrical Nanoha EXCEEDS Gun Blaze Vengeance, "ETERNAL BLAZE" from Magical Girl Lyrical Nanoha A's, "Innocent Starter" from Magical Girl Lyrical Nanoha.
Nana Mizuki performed the anime theme songs "CRIMSON BULLET" (Magical Girl Lyrical Nanoha EXCEEDS Gun Blaze Vengeance), "ETERNAL BLAZE" (Magical Girl Lyrical Nanoha A's), "Innocent Starter" (Magical Girl Lyrical Nanoha), "Kindan no Resistance" (Cross Ange: Rondo of Angel and Dragon), "ADRENALIZED" (HIGHSPEED Étoile), "Angel Blossom" (Magical Girl Lyrical Nanoha ViVid).
Nana Mizuki's first listed anime theme is "CRIMSON BULLET", the opening of Magical Girl Lyrical Nanoha EXCEEDS Gun Blaze Vengeance.