[3] Mizuno began his professional career with JEF United Chiba, with whom he won the J.League Cup in 2005 and 2006; he was named most valuable player of the 2006 competition.

Mizuno has 4 caps for the Japan national team, including two appearances as a substitute at the 2007 Asian Cup.

[4] Celtic's interest was confirmed by chief executive Peter Lawwell in January 2008 who explained that the club planned on signing Mizuno, if he was granted a work permit.

[8] After initially being denied a permit, Gordon Strachan took part in an appeal hearing in which he described his other Japanese import Shunsuke Nakamura as a "flawless performer" and "The best player I have ever worked with, and that includes [Kenny] Dalglish and [Gary] McAllister", and claimed that Mizuno was a young player of immense talent and potential.

Mizuno was a member of the Japan team for 2005 World Youth Championship where he scored a goal against Benin.