Imai started internationally for the first time at the Winter Asian Games 1990 in Sapporo . There he won bronze over 15 km classic and silver over 30 km freestyle. The following year he won the silver medal in the 30 km freestyle and the gold medal with the relay at the Winter Universiade in Sapporo. He made his debut in the World Cup at the beginning of the 1991/92 season in Silver Star , which he finished classically in 70th place over 10 km. At the following World Cup in Thunder Bay he got his first World Cup points with 12th place over 30 km freestyle and at the end of the season he achieved his best overall result with 44th place in the overall World Cup. His best result at the highlight of the season, the 1992 Winter Olympics in Albertville , was 25th in the 50 km freestyle. The following year he ran at the Nordic World Ski Championships in Falun on 80th place over 10 km classic, 59th place over 30 km classic and 49th place over 50 km freestyle. He also achieved 11th place with the relay. His best results at the 1994 Winter Olympics in Lillehammer were 20th place over 30 km freestyle and 14th place with the relay.
In the following year Imai came at the Nordic World Ski Championships in Thunder Bay on the 34th place over 10 km classic, on the 25th place over 30 km classic and on the 24th place in the pursuit. His best placements at the Nordic World Ski Championships in 1997 in Trondheim were 16th place over 50 km classic and 14th place with the relay and at the Olympic Winter Games 1998 in Nagano the 19th place over 10 km classic and seventh place with the relay . In the 1998/99 season he won the silver medal with the relay at the 1999 Asian Winter Games in Gangwon and took 56th place over 30 km freestyle, 50th in the pursuit, at the 1999 Nordic World Ski Championships in Ramsau am Dachstein 37th place over 10 km classic and 16th place over 50 km classic. In addition, he won there together with Katsuhito Ebisawa , Mitsuo Horigome and Hirofumi Watanabe the 14th place in the season. Two years later in Ramsau am Dachstein he achieved his best individual placement in the World Cup with ninth place in the 30 km mass start race and 44th place over 15 km classic at the 2001 Nordic World Ski Championships in Lahti , 30th place in the skiathlon , 21st place Place over 30 km classic and 12th place over 50 km freestyle and relay. His best results at the 2002 Winter Olympics in Salt Lake City were 12th place with the relay and sixth place over 50 km classic. The following year he won gold with the relay at the Asian Winter Games and ran at the Nordic World Ski Championships in Val di Fiemme to 25th place in the 30 km mass start race and ninth place with the relay and over 50 km freestyle. His last World Cup race he completed in December 2005 in Canmore , which he finished in 45th place in the 30 km mass start race.
Imai was seven times Japanese champion over 50 km (1991, 1997-2001, 2004), six times over 30 km (1991, 1993, 1996-1999), three times over 15 km classic (1997-1999), twice over 15 km freestyle ( 1998, 1999) and in pursuit (2000, 2004) and each once over 15 km (1991), over 10 km classic (2000). He also won five Continental Cups .
Participation in World Championships and Olympic Winter Games
winter Olympics
1992 Albertville : 25th place 50 km freestyle, 27th place 10 km classic, 29th place 15 km pursuit, 32nd place 30 km classic
1994 Lillehammer : 14th place relay, 20th place 30 km freestyle, 28th place 50 km classic, 40th place 10 km classic, 42nd place 15 km pursuit
1998 Nagano : 7th place relay, 19th place 10 km classic, 24th place 30 km classic, 28th place 15 km pursuit, 30th place 50 km freestyle
2002 Salt Lake City : 6th place 50 km classic, 12th place relay, 27th place 30 km classic mass start, 34th place 20 km skiathlon, 36th place 15 km classic
Nordic World Ski Championships
1993 Falun : 11th place relay, 49th place 50 km freestyle, 59th place 30 km classic, 80th place 10 km classic
1995 Thunder Bay : 11th place relay, 24th place 15 km pursuit, 25th place 30 km classic, 34th place 10 km classic
1997 Trondheim : 14th place relay, 16th place 50 km classic, 51st place 10 km classic, 55th place 30 km freestyle, 59th place 15 km pursuit
1999 Ramsau am Dachstein : 14th place relay, 16th place 50 km classic, 37th place 10 km classic, 50th place 15 km pursuit, 56th place 30 km freestyle
2001 Lahti : 12th place relay, 12th place 50 km freestyle, 21st place 30 km classic, 30th place 20 km skiathlon, 44th place 15 km classic
2003 Val di Fiemme : 9th place relay, 9th place 50 km freestyle, 25th place 30 km classic mass start
Japan
Kangwon