In 1362, Yoshimasa at the age of 13 became a steward by the recommendation of a dominant Shugo (provincial military governor), Doyo SASAKI who was a relative of the Shiba clan, and was appointed to Shugoshiki (provincial constable) of Ecchu Province in addition to Echizen Province.
康安2年/正平17年（1362年）、13歳の義将は斯波氏の縁戚であった有力守護の佐々木道誉の推薦で執事となり、越前国の他に越中国の守護職を与えられた。