Yamamoto made his international debut at the Nordic Junior World Ski Championships in Val di Fiemme, Italy . While he was not nominated for the Gundersen singles, he started in the sprint and team competition, but only reached the lower ranks. A year later he started in all three competitions of the Nordic Junior World Ski Championships in Almaty . In the Gundersen Singles over ten kilometers, he finished 25th, while he was fourteenth in the sprint and sixth with the team. On his debut in the Continental Cup , he immediately reached the top ten in eighth place in Park City . He also took this placement at the Gundersen Singles of the Nordic Junior World Ski Championships in Râşnov . In the sprint it was only enough for twentieth place, with the team he was seventh. After finishing in the top 10 in the Continental Cup three times in a row in January 2017 , Yamamoto was considered a co-favorite for his fourth Nordic Junior World Ski Championships , this time in Park City. He did not live up to expectations with a thirteenth place in the Gundersen individual and 26th place in the sprint. Nevertheless, he was appointed to the World Cup team for the first time in mid-February 2017 , but missed the points at the competitions in Sapporo .
In the winter of 2017/18, Yamamoto regularly made it into the points in the Continental Cup . He also competed in the Continental Cup at the beginning of the 2018/19 season . He reached the podium for the first time in late December 2018 when he finished third behind Taylor Fletcher and Julian Schmid in Park City . After further strong results, he was promoted to the World Cup team in January 2019 and immediately won his first World Cup points. In the following weeks Yamamoto regularly reached the points in the World Cup, but was not nominated for the World Championships in Seefeld . Yamamoto finished the season in fourteenth place in the overall Continental Cup ranking and 48th place in the 2018/19 World Cup overall ranking .
At the start of the Grand Prix , Yamamoto won the provisional competition jump in Oberwiesenthal , which demonstrated his strong jumping form. He also confirmed this performance in the competition when he finished third in the mass start in Klingenthal a few days later . In the winter of 2019/20, Yamamoto was part of the Japanese World Cup team from the start and developed into a key player in his ailing nation. On the first competition weekend in Ruka he was ninth in the top 10. As the season progressed, the strong jumper consistently achieved points. At the end of January 2020, he surprisingly finished third with Akito Watabe , Hideaki Nagai and Yoshito Watabe in the relay.
Japan
