 In late 2002 he scored the winner in a 2-1 victory against Frösö IF U-19.Ersboda were playing in the Swedish Division Four at the time, but with Mumuni's help were promoted to the third division after winning the league in 2003.In 2004, Mumuni's final season with Ersboda and in football, he scored five times in 12 games, to help Ersboda to an impressive third-place finish in the club's first season in the third division.