Leto is the god of the Sun worshiped by the inhabitants of Reole. Brought to the poor eastern town by the false Letoist prophet Cornello, the religion based around this sun deity was designed to inspire the townspeople into participating in an attempted coup d'etat without the fear of death to hold them back. Though Cornello was ousted by the Fullmetal Alchemist and his miracles exposed as the effects of a false Philosopher's Stone, the remnants of Letoism created a schism in Reole that caused a great deal of unrest and bloodshed, which fell perfectly into the preconceived plans set up by the Order of the Ouroboros - the same group who had sent Cornello from the start.
When the story returns to Reole, it becomes apparent that the gigantic statue of Leto that Fullmetal had created to defeat Cornello has become a major town landmark. Additionally, it seems the sun god himself has some significance to the Promised Day, as a solar eclipse appears to play a large role in Father's endgame.
- It is interesting to note that, in Greek mythology, Leto was a lover of Zeus and gave birth to the twins Artemis and Apollo, the Greek sun god.
- The title page for Chapter 102 has the Elric brothers sitting atop a giant Leto statue, likely the one Edward transmuted at the start of the series.