Prior to joining the Minnesota-Duluth Bulldogs, she participated for Cal Selects Hockey Club from 1999–2003, and was recognized as the Cal Selects Player of the Year for 2002–03. Koizumi competed for the Minnesota-Duluth Bulldogs and finished her career ranked seventh all-time on the Bulldogs scoring list. She accumulated 155 points. In 2006–07, she led the Bulldogs with six game-winning goals. Koizumi was also a two sport star, as she also participated in softball with the Bulldogs. In her senior season, Koizumi was also Bulldogs captain. The final game of her NCAA career was the championship game of the 2007 NCAA women's Frozen Four. During the semifinal match of the Frozen Four tournament, Koizumi registered two goals and an assist as the Bulldogs bested Boston College in double-overtime.
USA Hockey
Koizumi has attended the USA Hockey Women's National Festival from 2004 to 2007. In September 2007, Koizumi was selected to be part of the American contingent competing in the 2007 Four Nations Cup, held in Leksand, Sweden. From 2004 to 2006, Koizumi was a member of the United States U-22. In addition, she claimed a gold medal at the roller hockey world championships in July, 2006. At the 2008 IIHF World Women's Championship, Koizumi was part of the gold medal winning roster. She has also represented Team USA at three Women's World InLine Hockey Championships, from 2005 to 2007 respectively. That included a gold medal in Detroit in 2006 and a silver medal in France in 2005.
CWHL
Koizumi played in the CWHL with the Montreal Stars and the Boston Blades. In 2010, the Stars reached the 2010 Clarkson Cup semi-finals. The following year, Koizumi was part of the 2010–11 Boston Blades season. She helped the Blades win the Clarkson Cup in 2013 and 2015. In the second last game of the Boston Blades regular season in 2013–14, Koizumi logged her 50th career point with the Blades. Of note, this makes her the first player to register 50 points with the Blades franchise.
NWHL
On July 9, 2015, Koizumi signed with the Connecticut Whale of the NWHL. Competing with the Whale in the NWHL's first game on October 11, 2015, she would score the first goal in franchise history and the first goal in league history. On November 14, 2015, Koizumi was named the captain of the Connecticut Whale, with Kaleigh Fratkin as the assistant captain. On September 12, 2016, Koizumi announced her retirement and accepted a coaching position at Ohio State University.
Coaching career
After graduation, Koizumi joined the Bulldogs coaching staff. On September 27, 2010, Koizumi was hired as an assistant for the Yale Bulldogs women's ice hockey program. She worked for Joakim Flygh, who was an assistant at Minnesota-Duluth while Koizumi played there until 2016. After a one-year stop at Ohio State, Koizumi became the associate head coach at Vermont. In addition, Koizumi has also served as a head coach at multiple USA Hockey National Girls’ Hockey festivals, working with the U14 team in Rochester, in 2010; the U16 team in St. Cloud, Minnesota, in 2009 and 2010; and the U17 team in Lake Placid, in 2007. She also served as an evaluator at USA Hockey's Pacific District tryouts in Seattle, from 2007 through 2009
Career stats
NCAA
USA Hockey
Awards and honors
2002–03 Cal Selects Player of the Year
2003–04 WCHA All-Rookie Team
2006–07 All-WCHA Third team selection
2007 Frozen Four All-Tournament Team
Personal
In May 2007, Koizumi graduated from Minnesota-Duluth with a major in psychology and a minor in coaching. She was eligible for the NCAA Post Graduate Scholarship and earned her Masters of Education degree in 2009. Koizumi is known by the nicknames 'Zumi', 'Tsunami', 'Cali'
