Mizue Hoshi took part in FIS races from August 2000 , where she achieved several victories straight away. In the winter of 2000/01, the first appearances in the Far East Cup and in the European Cup followed and in March 2001 she won the Japanese championships in Super-G. Another four national titles followed by 2011. From 2002 to 2005 she took part in four junior world championships and achieved the best results in 15th place in slalom 2005 and two 18th places in giant slalom and combined in 2004 . Mizue Hoshi has been regularly at the start in the Far East Cup since winter 2003/04, where she has been one of the strongest runners ever since. She celebrated her first victory on March 14, 2005 in the slalom of Shigakōgen , three more victories followed in 2006, 2008 and 2009. In the winter of 2010/11 she achieved seven victories in the Far East Cup. From December 2004 she also took part increasingly in European Cup races. With ninth place in the knockout slalom in Bottrop in November 2005 and tenth place in the slalom in Garmisch-Partenkirchen in February 2006, she achieved her first top 10 results in this racing series. After she had not competed in the winter of 2006/07, she took part in most of the slalom and giant slalom races in the European Cup in the 2008/09 and 2009/10 seasons and achieved another three top 10 placements in these two years.
The Japanese has competed in the World Cup since November 2004, mainly in slalom races and less often in giant slalom. However, so far she has not been able to qualify for the second round of the top 30 in any of her World Cup races. At World Championships and Olympic Games, however, she was already in the fastest 30s several times. At the 2005 World Championships in Bormio , she achieved the best result in major events with 21st place in the slalom, and she was 34th in the giant slalom. At the 2006 Winter Olympics in Turin , she finished 27th in slalom. At the 2009 World Championships , she narrowly missed qualifying for the second run in slalom and was rated 27th. In the giant slalom she was eliminated. Shortly after this World Cup, the Nippon Sport Science University student won the gold medal in giant slalom at the 2009 Universiade in Harbin, China . At the 2011 World Championships in Garmisch-Partenkirchen , she finished 40th in giant slalom, while she failed in slalom.