Jun Manjoume is an arrogant Duelist who serves as one of Juudai Yuuki's rivals throughout the series. Jun is considered Juudai's main rival in the same effect that Seto Kaiba is the rival of Yuugi Mutou. The two have Dueled one another a total of seven times throughout the seasons of the anime. Through his evolution, he goes from being a Duelist who only respected powerful cards to a Duelist who believes that there can be effectiveness in any card.
In the manga, Jun originally serves much the same purpose as in the anime, but later becomes a deuteragonist.