Hosoyama made his international debut in 2002 in the Ski Jumping Continental Cup . Already in his first competition on January 11, 2002 on the Miyanomori hill in Sapporo he achieved a surprisingly good placement with fourth place. At the Junior World Championship in Schonach in 2002 , he jumped to 49th place. After that he only jumped in jumping in Japan until the end of 2006, but could not achieve any top placements. In January 2007 he started at the Winter Universiade in Pragelato . He reached 11th place on the normal hill and 13th place on the large hill. In the team competition he won the bronze medal together with Yoshihiko Osanai and Shūji Endō . On January 25, 2008 Hosoyama started his first jumping in the World Cup . However, he could not reach the points in the two competitions he completed. On January 9th, 2009 he was able to achieve his only podium place in the Continental Cup with third place in jumping on the Miyanomori hill in Sapporo. With a few exceptions, he has only competed in FIS races and in the FIS Cup in Japan since March 2009 .