Yumoto started in March 2002 at the Continental Cup in Zaō for the first time in an international competition. In January of the following year he got his first assignment in the ski jumping world cup in Sapporo . In the following years he only started in jumping competitions in Japan. After he was able to jump into the points at the World Cup in Sapporo in February 2005, he started a little later in Continental Cup competitions in Europe. In 2006, however, he started again only in Japan and only took part in competitions in Europe again in 2007, after he had achieved his first podium placement at the Continental Cup in Sapporo with a third place. He also took part in the summer jumping of the Continental Cup in July 2007. In these he was always able to place himself in the top fifteen, which is why he was used in the competitions of the Summer Grand Prix 2007 in August and was able to collect several points there.
In the winter of 2007/08 he took part in the World Cup throughout and was mostly able to achieve placements in the midfield. In summer 2008 he started again at the Grand Prix. At the season opener of the 2008/09 World Cup season in Kuusamo he reached eighth place. On December 14, 2008, he surprisingly won his first World Cup competition in Pragelato in a competition characterized by heavy snowfall, which had to be abandoned after the first round.