In the future, mankind has developed a multi-sport tournament known as Iron League, using artificially intelligent robots as the players instead of humans. The competition is very popular. However, its main support comes from the Dark Organization, a group that produces cheating Iron Leaguers that use dirty and violent tactics in games as a sure ticket for fame and popularity. While the sports community has been turned into a dangerous and (figuratively) bloody contest, Silver Castle, the team with the lowest winning ratio, tries to preserve true sportsmanship by playing sports by their original rules without any cheating or violence. The team's fate as well as the fate of the Iron League itself is changed when two Iron Leaguers - Mach Windy, Dark Prince FC's former ace striker and Magnum Ace, a mysterious but skillful baseball-playing Leaguer - join Silver Castle, and gradually lead the team back to its forgotten glory. It's not all fun and games, however; as the story goes on, it is revealed that the Iron League is actually a front for something far more sinister...

(Source: TV Tropes)