Masahiro Akimoto's first jumping was the start of the first ever ski jumping World Cup on December 30, 1979 in Oberstdorf . In addition, this was the opening competition of the Four Hills Tournament 1979/80 . Akimoto came in 61st place in jumping on the large hill. On January 4th, 1980 he came in 23rd place in the jumping in Innsbruck and won World Cup points for the first time. On January 13th, he won the jumping on his home hill in Sapporo and was on the podium for the first time. At the 1980 Olympic Winter Games and the associated Nordic World Ski Championships in Lake Placid , Akimoto managed to jump to 4th place on the normal hill. He was tenth on the large hill. On March 24, 1980 he was able to win a World Cup competition for the second time at the World Cup in Štrbské Pleso , after he had always jumped into the top 15. The 1981/82 World Cup season began for Akimoto with a 3rd in Cortina d'Ampezzo . He finished the following World Cups only on mediocre placements. Only at the jumping in Sapporo could he prove his qualities again with a 3rd and a 9th place. At the Nordic World Ski Championships in Oslo in 1982 , however, he only managed a 41st place on the normal hill and a disappointing 53rd place on the large hill shortly afterwards. He then took a break from competition for two years.
On January 21, 1984 he started Sapporo again in the ski jumping World Cup and was able to win this jumping straight away. In the second competition he came in 3rd place. At the 1985 Nordic World Ski Championships in Seefeld in Tyrol , he was able to improve his performance from 1982 and came 21st on the normal hill and 32nd on the large hill. In team jumping he reached 6th place together with Yatarō Watase , Akira Satō and Chiharu Nishikata . The first world cup competition after the world championship took place again in Sapporo. Also this time Akimoto won this jumping and won the fourth jumping in his career. However, it was his last victory. After several top 10 placements, he ended his active ski jumping career on March 1, 1986 after a 10th place on the normal hill in Lahti .
In the national general election in 2005 Akimoto ran for Muneo Suzuki's regional party Shinto Daichi , in which he also became vice-chairman, in the 1st constituency of Hokkaidō, the constituency of ex-governor Takahiro Yokomichi , but was clearly subject to the candidates of the established national parties.