Quick answer — Maaya Uchida and Soma Saito performed 1 anime theme, including "Kokoro no Kagi" from Astro Note.
Maaya Uchida and Soma Saito performed the anime theme songs "Kokoro no Kagi" (Astro Note).
Maaya Uchida and Soma Saito's first listed anime theme is "Kokoro no Kagi", the ending of Astro Note.