At the 2009 World Championships in London, Koko Tsurumi competed a historic performance to win the individual all-around bronze medal.

During event finals, Tsurumi won the silver medal on uneven bars and placed 6th on balance beam.

Tsurumi is the first Japanese woman gymnast to win a World Championships medal in 43 years.

At the 2010 World Artistic Gymnastics Championships, Tsurumi experienced problems with consistency and failed to make any event finals and placed 21st in the All Around, behind countrywoman Rie Tanaka.

She made her elite comeback at the 2015 WOGA Classic in Plano, Texas, scoring 15.000 on bars and 13.850 on beam.