Muta is on Goro Shigeno's junior high teammates and a member of Mifune East's Baseball Club in the Mifune East Arc. He was one of the bullies who lied about being the team's "secret weapon" to explain why he wasn't part of the starting line-up due to his perceived lack of skill.
He later pinch-hits in the game against Tomonoura so he could get a chance to play.
In the World Series, he goes to the United States with Yamane and Oobayashi to watch the game with Shimizu and Goro's high school teammates. It is revealed that he and Oikawa continued to play recreation baseball in their free time.
He is last seen in Goro and Kaoru's wedding photo, along with Goro's former Japanese teammates.