Simon Muran is the Yu-Gi-Oh! Forbidden Memories incarnation of Shimon Muran, a character from the manga and anime. Simon is the prince's tutor, attendant and card mentor. He taught the prince how to play the card game.
Depending on the player's actions, Simon can tell the prince the story of how the card games were used to Summon powerful monsters, causing chaos, therefore restricting the use of the cards to their kingdom. Also depending on their actions, they may duel him.
When Heishin attacked the palace, claiming to have uncovered great power, Simon is alerted. Simon, not fond of Heishin, confronted him, resulting in Simon being badly beaten. When the prince arrived, Heishin demanded to know where the Millennium Puzzle was. Simon secretly gave the Puzzle to the prince, telling him to run. Unable to escape, the prince was forced into a Duel with Heishin. After the prince lost, Simon convinced him to shatter the Puzzle.
Simon sealed the prince's soul within the broken Puzzle, leaving him on a mission to collect the power of the Millennium Items before returning to their time. Upon returning to his time, Simon bid the prince good luck and then faded out of existence.
Simon's Deck is composed mainly of low Level weak Monster Cards.