Quick answer — May'n performed 2 anime themes, including "Brain Diver" from Phi Brain: Puzzle of God, "Re:REMEMBER" from M3: Sono Kuroki Hagane.
May'n performed the anime theme songs "Brain Diver" (Phi Brain: Puzzle of God), "Re:REMEMBER" (M3: Sono Kuroki Hagane).
May'n's first listed anime theme is "Brain Diver", the opening of Phi Brain: Puzzle of God.
