Quick answer — Marina Horiuchi performed 1 anime theme, including "Mizukagami no Sekai" from The Devil is a Part-Timer! Season 2.
Marina Horiuchi performed the anime theme songs "Mizukagami no Sekai" (The Devil is a Part-Timer! Season 2).
Marina Horiuchi's first listed anime theme is "Mizukagami no Sekai", the ending of The Devil is a Part-Timer! Season 2.