His international debut came at the 2006 IAAF World Cross Country Championships in Fukuoka, where he was 49th in the men's long race. In 2007 he was second over 10,000 metres at the Japanese Athletics Championships then equalled the Japanese collegiate record over 5000 m at the KBC Night of Athletics (running a time of 13:19.00 minutes). He finished twelfth in the 10,000 m at the 2007 World Championships. Takezawa was runner-up in the 5000 m at the 2008 Japanese nationals and was selected for the Japanese Olympic team: he ran in the first round of the 5000 m and finished twenty-eighth in the 10,000 m at the men's 10,000 metres.