Miwa played his Junior hockey primarily for the Thornhill Thunderbirds of the Metro Junior B Hockey League in Toronto. In his final season of Junior hockey his Thornhill team won the league championship over the Wexford Raiders in the 1989-90 season.
Miwa started his pro career in the city of Sapporo, Hokkaido, Japan where he played for the Snow Brand Ice Hockey Team for 6 seasons. He then moved on to Nikko, Tochigi, Japan to play for the Nikko Icebucks and stayed there for another 5 seasons. His final two seasons saw him play for the Oji Paper Ice Hockey Team in Tomakomai, until his retirement after the 2006-07 season. He was granted Japanese citizenship in 2002, which allowed him to represent Japan at the 2002 World Championships in Jönköping, Sweden, the 2003 World Championships in Helsinki, Finland, and the 2004 World Championships in Prague, Czech Republic.