Kojima started ski racing when he was 7 years old and raced for the next 16 years. After which he decided to switch and took up snowboard racing and won the Japanese National Championship 3 times. He was a member of the national team for 6 years and competed at World Championship and World Cup. After retiring from his racing career he became a high school teacher. He formed the first Japanese school snowboard team and promoted snowboarding to Japanese sports education. He founded Kojima Academy in Furano in 2002 and focused on his snowboard racing program. His program coached young snowboard athletes from around the world in Japan, New Zealand and Europe. He had a total of 6 athletes that went to Salt Lake City Olympics, Torino Olympics, and Vancouver Olympics. He again enjoyed olympic success with an athlete gaining a silver medal at the Sochi olympic games.